We want to use the markdown syntax for highlighting

Github has cool syntax highlighting but only available for
markdown documents. Since we're a gem, we want that advantage.
We want to use markdown for syntax highlighting

In addition to switching to Markdown I've:

  - Adding a contributors guide
  - Cleaned up the writing and paragraph positioning
  - Cleaned up a few of the code examples
  - Added code markers to some of the in-paragraph code
  - Linked properly to the resources referenced
Merge pull request #54 from harukizaemon/switching-to-markdown-for-readme

Switching to markdown for readme