magit-read-stash: actually use PROMPT argument

(cherry picked from commit f9739c5d680053de831fc2bbec9b21ab90d24217)

Conflicts:
	magit.el
move definitions of functions and variables used for log washing
remove dead function magit-wash-typechange-section

By the way, the functionality this intended to provided will be
implemented for real soon.
magit-mode-setup: abort if not inside a repository

Previously we ended up setting `default-directory' to nil in
`magit-mode-init'.  While doing that is always a bad idea in this
case the result was fatal; for some reason it caused Emacs to enter
an endless loop and neither C-g nor ESC where able to break it.

Close #1255.
move definitions of functions and variables used for diff washing

In preparation of major refactoring move definitions of functions and
variables used for diff washing.  The old location has never made
much sense.

Only move the functions and variables that implement "diff" and "hunk"
washing, and leave the "raw diff" functions where they are now.  They
are not going to be refactored.  This extra washing cycle will be
removed without a replacement because it has no benefits but many
downsides.
magit-wash-diff: absorb utility funtions

Yes, this is spaghetti code but having the spaghetti split
across multiple pots actually makes it harder to turn this
mess into a good meal.
rename magit-{ => diff-}highlight-{line- => }whitespace
magit-diff-statline-re: new constant
magit-wash-diffs: don't wash if there ain't no laundry
Merge branch 'faster-diff-2'
magit-mode-setup: fix scope issue when evaluating buffer form
use official travis-ci button again

The button from shields.io takes to long to be updated.
magit-git-executable: use executable-find when initializing value

This hopefully give a slight performance bust.

The downside is that the headers in the process buffer get longer
and that the "interesting parts" might end up being truncated.

Still I hesitate to add an option to hide the full path and the
`magit-git-standard-options'; when instructing users to provide
the information required to debug some issue there would be one
more thing that we would have to make sure they actually did.

If `executable-find' fails to find Git then fallback to "git".
magit-git-executable: use git.exe on Windows

On Windows, explicitly use the "git.exe" executable instead of "git".
If that fails accept any "git".

It has been reported that this gives a considerable speedup.  I don't
know Windows but it appears that when asking for a "foo" one might get
a "foo.exe" or a "foo.cmd" or a "foo".  It also appears that "git.cmd"
is earlier on the `exec-path' than "git.exe", or that the former is
preferred for some other reason.
Merge branch 'git-executable'
magit-revert-buffers: revert buffers in emacs 24.4

In Emacs 24.4, when `auto-revert-use-notify` is t, but auto-revert is
not enabled for current buffer (auto-revert-notify-modified-p remains
nil), `auto-revert-handler` will not revert the buffer. Setting
`auto-revert-mode` to t for buffer to be reverted will make
 `auto-revert-handler` effective.
Merge pull request #1290 from achitu/master

magit-revert-buffers: revert buffers in emacs 24.4
AUTHORS.md: update list of contributors
teach magit-stage-item to add submodules
magit-wash-diff-section: revert accidental face change

Not that I think we need to use different faces here but stopping to do
so was not intentional.