allow overriding lib/*.zsh in custom/lib
Merge pull request #3344 from wrboyce/custom-lib

allow overriding lib/*.zsh in custom/lib
Change upgrade remote to 'upstream'
Show literal command in title instead of unaliased command
Add 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
Remove add-zsh-hook usage from doubleend theme
Syntax simplified in doubleend theme
Add battery gauge custom plugin, dependency of doubleend theme.
Change directory checking syntax in batcharge plugin
Include batcharge.py into batcharge function

This prevents a not found error when the batcharge.py script cannot be
found, which happens whenever we checkout a point in time where the
batcharge plugin is not there.

By including it directly into the batcharge plugin function we achieve
both the disappearance of the error mentioned above and ensure a fully
functioning batcharge plugin (as long as the batcharge function is
still there).

An alternative solution was to put a check for the batcharge.py script
inside the batcharge function, before calling it with python. This,
however, wouldn't mantain the plugin's functionality.

A desirable future change will be to translate the python script into
zsh code, so as to avoid running a separate process in every call of
the batcharge function and remove the necessity of a python binary.
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)
Add ragekill plugin
Don't require toilet in ragekill plugin

In systems without root permission you can't install toilet. This change
lets you use the flip script included within the ragekill plugin if
toilet is not found, to flip the process name instead.

It also changes the naming of the plugin in a couple more places which
weren't changed at the time, and redoes some logic paths to optimize
and clean up the plugin.
Minor fixes in INSTALL.md in ragekill plugin
Add z custom plugin & update upstream sources