Make readme headings markdown compliant.

README.md

@@ -1,4 +1,5 @@
 WHAT?
+====================
 
 - Run the test/spec your cursor is currently on
 - Run the context your cursor is currently in
@@ -12,6 +13,7 @@ This plugin currently supports
  - shoulda
 
 HOW?
+====================
 
 Use any of the commands below. Map them to shortcuts
 in your .vimrc for easy access.
@@ -21,15 +23,18 @@ in your .vimrc for easy access.
  - RunAllRubyTests - run all the tests/specs in the current file
 
 INSTALL
+====================
 
 Put the contents of this directory into your pathogen bundle. That's it!
 
 REQUIREMENTS
+====================
 
 - vim with ruby support (compiled +ruby)
 - [vimux](https://github.com/benmills/vimux)
 
 CONTRIBUTORS:
+====================
 
 - [Drew Olson](https://github.com/drewolson)
 - [Paul Gross](https://github.com/pgr0ss)