Added git mode support for merging, rebasing, and bisecting

<B> Designates Bisecting
>M< Designates Merging
>R> Designates Rebasing
Merge pull request #2633 from redsunsoft/agnoster-theme-git-mode-addition

Added git support for merging, rebasing, and bisecting to agnoster theme
Changed upgrade remote to 'upstream'
Added doubleend theme from Nettuts+

This commits have been squashed:
- Added doubleend theme from Nettuts+
- Better git prompt on doubleend theme
- Syntax fixes, precmd inside $PROMPT to work with Ctrl+L
- Refactoring doubleend theme
- Cleanup, comments added
- Variables wrapped in double quotes in spacing()
- Modified $PROMPT to single line; cleanup.
- Modified CTRL+L behaviour to execute precmd() prompt line
- Renaming functions. Fixes git autocompletion
- Theme refactor. Works on CTRL+L and resizing
- Simplification of if-else
Changed autocorrection options in oh-my-zsh

Added more granularity to correction options:
- Disable correction at all
- Disable correcting arguments (and aliasing commands 'nocorrect'-ed)
fix gwip alias for some BSD flavors, fixes #2692
Add return codes to agnoster theme

This adds the ability to show the return code of every process in a pipe chain,
as long as at least one of them returns a value other than 0.
There is the option to disable this behaviour as well.
Merged from robbyrussell/oh-my-zsh/pull/2573 (by @diogovk)
cosmetic (could not resist)
Show literal command in title instead of unaliased
Merge remote-tracking branches 'kemko/patch-1', 'ncanceill/fix-gwip' and 'LFDM/cleaning_lib' into dev

Conflicts:
	lib/history.zsh
version 0.1 from current upstream project https://github.com/mbauhardt/oh-my-zsh-bootstrap
bundle the plugin into the omz function
added completion to omz function
really enable (hardly possible to really disable)
pre-enable theme from .zshrc
use a shorter plugin name
updated readme
updated plugin name
send tabs into space
add myself as maintainer