Added new entries to global gitignore
Numerous changes to .vimrc

- Added settings for Solarized theme
- Added settings for NERDTree plug-in
- Changed how section headings are displayed
- Etc...
Added new key bindings to .zshrc
Added .tmux.conf to repo
Added new entry to .gitignore_global
Added new vim bundles as git submodules

Added the following:

- vim-colors-solarized
- vim-gitgutter
- vim-markdown