Fix formatting bugs in README.md
Merge pull request #16 from dmcglinn/format

Fix formatting bugs in README.md
Use .R file extension

This is more common and plays better with GitHub.
Change to R style license indication

Fixes #18.
Merge pull request #20 from ethanwhite/r-style-license

Change to R style license indication
Merge pull request #19 from ethanwhite/file-extension

Use .R file extension