Slightly better README

Author: WillJCJ

README.md

@@ -4,8 +4,24 @@
 
 - bash completion for parameter names
 - Distribute as a release.
+- Common SSM service instead of duplicated in both.
 - Write tests!
 
-Usage
+## Usage
 
-    param [copy|list]
+Copy a parameter to your clipboard:
+
+    $ param copy parameter_name
+    Copied parameter_name to clipboard.
+
+Get a sorted list of parameters in SSM with optional prefix(es):
+
+    $ param list
+    parameter_name1
+    parameter_name2
+    ...
+
+    $ param list prefix1 prefix2 ...
+    prefix1.dev.password
+    prefix1.prod.password
+    prefix2.key