Add Rayon for parallel file checking

Now we're almost entirely IO bound, rather than having to wait to
read and search through files one at a time.

Cargo.lock

@@ -67,6 +67,12 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "clap"
 version = "2.33.1"
@@ -82,12 +88,53 @@ dependencies = [
  "vec_map",
 ]
 
+[[package]]
+name = "const_fn"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28b9d6de7f49e22cf97ad17fc4036ece69300032f45f78f30b4a4482cdc3f4a6"
+
 [[package]]
 name = "constant_time_eq"
 version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "245097e9a4535ee1e3e3931fcfcd55a796a44c643e8596ff6566d68f09b87bbc"
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dca26ee1f8d361640700bde38b2c37d8c22b3ce2d360e1fc1c74ea4b0aa7d775"
+dependencies = [
+ "cfg-if 1.0.0",
+ "crossbeam-utils 0.8.1",
+]
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94af6efb46fef72616855b036a624cf27ba656ffc9be1b9a3c931cfc7749a9a9"
+dependencies = [
+ "cfg-if 1.0.0",
+ "crossbeam-epoch",
+ "crossbeam-utils 0.8.1",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1aaa739f95311c2c7887a76863f500026092fb1dce0161dab577e559ef3569d"
+dependencies = [
+ "cfg-if 1.0.0",
+ "const_fn",
+ "crossbeam-utils 0.8.1",
+ "lazy_static",
+ "memoffset",
+ "scopeguard",
+]
+
 [[package]]
 name = "crossbeam-utils"
 version = "0.7.2"
@@ -95,7 +142,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
 dependencies = [
  "autocfg",
- "cfg-if",
+ "cfg-if 0.1.10",
+ "lazy_static",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "02d96d1e189ef58269ebe5b97953da3274d83a93af647c2ddd6f9dab28cedb8d"
+dependencies = [
+ "autocfg",
+ "cfg-if 1.0.0",
  "lazy_static",
 ]
 
@@ -105,7 +163,7 @@ version = "2.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "13aea89a5c93364a98e9b37b2fa237effbb694d5cfe01c5b70941f7eb087d5e3"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "dirs-sys",
 ]
 
@@ -115,19 +173,25 @@ version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "afa0b23de8fd801745c471deffa6e12d248f962c9fd4b4c33787b055599bde7b"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "redox_users",
  "winapi",
 ]
 
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
 [[package]]
 name = "getrandom"
 version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7abc8dd8451921606d809ba32e95b6111925cd2906060d2dcc29c070220503eb"
 dependencies = [
- "cfg-if",
+ "cfg-if 0.1.10",
  "libc",
  "wasi",
 ]
@@ -153,14 +217,59 @@ version = "0.2.70"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3baa92041a6fec78c687fa0cc2b3fae8884f743d672cf551bed1d6dac6988d0f"
 
+[[package]]
+name = "memoffset"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "157b4208e3059a8f9e78d559edc658e13df41410cb3ae03979c83130067fdd87"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "num_cpus"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05499f3756671c15885fee9034446956fff3f243d6077b91e5767df161f766b3"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
 [[package]]
 name = "rack"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "rayon",
  "term",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b0d8e0819fadc20c74ea8373106ead0600e3a67ef1fe8da56e39b9ae7275674"
+dependencies = [
+ "autocfg",
+ "crossbeam-deque",
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ab346ac5921dc62ffa9f89b7a773907511cdfa5490c572ae9be1be33e8afa4a"
+dependencies = [
+ "crossbeam-channel",
+ "crossbeam-deque",
+ "crossbeam-utils 0.8.1",
+ "lazy_static",
+ "num_cpus",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.1.56"
@@ -187,9 +296,15 @@ dependencies = [
  "base64",
  "blake2b_simd",
  "constant_time_eq",
- "crossbeam-utils",
+ "crossbeam-utils 0.7.2",
 ]
 
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
 [[package]]
 name = "strsim"
 version = "0.8.0"