Add Ruby 2.0 to travis list.  Also removing bundler from requirements
Fix RBX version name
Upgrade rdiscount to fix JRuby tests
Move to Ruby 2.0 and new .ruby-version files
Use a pure Ruby markdown library
Goodbye 1.8.7
Init method cleanup - Closes #6

- Make redis connection optional via options hash
- Raise ArgumentError if redis object is passed in outside the options hash