Add usage README

README.md

@@ -0,0 +1,20 @@
+# Rack 0.1
+Like Ack but in Rust
+
+```
+USAGE:
+    rack [FLAGS] <pattern> [path]
+
+FLAGS:
+        --no-gitignore    Include results that are specified in .gitignore
+        --help            Prints help information
+    -i                    Ignore case when looking for matches
+    -h                    Omit file names in results
+    -o                    Only print matched text
+    -V, --version         Prints version information
+
+ARGS:
+    <pattern>    The pattern you're looking for
+    <path>       Path to search in [default: ]
+```
+