Manage gems + Ruby @ current stable versions w/RVM

* update to modern, supported Ruby 2.0 version
* update gems to current versions using Bundler
* make jekyll configs confirm to current version
* switch deb package dependencies to cross-platform rvm
* ignore bundled dependencies
* some README mods as per @harding + @saivann
Merge pull request #266 from jm3/master

Manage gems + Ruby at current stable version(s)