Update README with usage info

README.md

@@ -2,10 +2,30 @@
 
 Haskell client for tldr
 
-![tldr](https://cloud.githubusercontent.com/assets/737477/24076451/2a5a604c-0c57-11e7-9bf7-13d76e8e7f12.png)
-
 ## Installation
 
 1. [Install stack](https://docs.haskellstack.org/en/stable/README/#how-to-install)
 2. Clone this repo  (TODO: Publish this to Stackage)
 3. `stack install`
+
+## Usage
+
+``` shellsession
+$ tldr --help
+tldr - Simplified and community-driven man pages
+
+Usage: tldr [-v|--version] [--update] COMMAND
+  tldr Client program
+
+Available options:
+  -h,--help                Show this help text
+  -v,--version             Show version
+  --update                 Update tldr pages
+  COMMAND                  name of the command
+```
+
+## Snapshot
+
+![tldr](https://cloud.githubusercontent.com/assets/737477/24076451/2a5a604c-0c57-11e7-9bf7-13d76e8e7f12.png)
+
+