Improve some formatting

This commit mostly wraps lines correctly. Among other changes are:

  - Fixed some typos
  - Aligned some code
  - Removed unnecessary `return`s
  - Converted some text in comments to YARD tags (@see)

All of these changes are intended to be cosmetic with the goal of
improving the readability of the code and documentation.

I only hit a few files in this commit, but I figured it was worth
committing anyway.
Merge pull request #56 from lencioni/documentation

Improve some formatting
Add screencast
Tweak README
Tweak README again
Remove image