Consolidate zshrc, profile, and aliases

These three files were just clutter for what could be a single file
configuration. Now, in order to override or add to anything on a local
machine, you may add them to ```$HOME/.zshrc.local```.
Mac OS X and Linux have the same gcc path

Yosemite and Linux now can compile Ruby with the built-in
gcc compiler. Yay for fewer conditionals!
Tweak display for tmux window status