Configure OS X Vim to use Molokai color scheme

Molokai source: https://github.com/tomasr/molokai
Change colors for Git diff and patching (OS X)

`git diff`
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* Change hunk headers to `magenta dim`.
* Change hunk function headers to `white dim`.

`git add --patch`
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* Change prompt to white.
* Change help to yellow.

Miscellaneous
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* Remove trailing whitespace.
Move Postgre.app to front of Bash PATH (OS X)
Configure Bash to use default colorscheme (OS X)