Package changes: Ruby 2.1, GCC, doxygen

* Ruby 2.1.1 added
* GCC removed, everything compiles with clang now
* doxygen added – we don't need a custom version any longer
Tmux: Adjustments for tmux

This is a blast from the past, fixed it a while ago because it threw
warnings
Git & Tig Config added
RVM always overwrites this poor alias :broken_heart:
Bundler Config added: Use system V8, 3 jobs and pry as console
RVM shenanigans