Run the tmux plugin install iff possible

Various updates and minor fixes

Git
- use fugitive for merges
- git scripts (new, weekly)
- better swapfile ignore pattern

Vim
- turn on linenumbers by default
- plugin updates
- 'K' program fix for vim help

Bash
- color-test script
- venv info in prompt
- shorten default PS1

Tmux
- enable mouse
- bindings, style, &c.

Integrate gitsh

Update vimrc, vim plugins, colors, initial tmux

Merge pull request #105 from benknoble/dev-1.4

1.4 Features

Vim key improvements

A couple of bugfixes

Update vim plugins

Update vim plugins

Update script improvement