magit-delete-directory: use copy of tramp-compat-delete-directory

Previously we determined the number of arguments `delete-directory'
accepts at compile time and defined this function accordingly.  Now
`magit-delete-directory' assume `delete-directory' supports RECURSIVE
and only if that causes `wrong-number-of-arguments' it does the
recursive delete itself.

This fixes #684.  The old code broke on 24.3.50 and also was more noisy
and ugly than what we have now.
move travis indicator below heading

Otherwise the placeholder text is displayed using the same size as the
real heading, until the image has been loaded.
Fix default-directory issue with magit-grep.

As of now, magit-grep doesn't set the default-directory variable
correctly when creating the *Magit Grep* buffer.  This is especially
problematic if the user tries to use the file name / line number pair as
a link.
travis: allow build on emacs-snapshot to fail

This is yet another kludge necessary to prevent travis from always
failing (without there actually being a problem with magit).

The failure is this:

  $ elpa-get mocker cl-lib
  ...
  Wrong type argument: arrayp, mocker

Actually that was the failure yesterday, currently building on
emacs-snapshot does not even produce any output or terminate.
This might be unrelated though.

This might be related to recent struct-ification of package.el
in Emacs-24.3.50.
Merge pull request #699 from sanjoy/default-dir-in-magit-grep

Fix default-directory issue with magit-grep.
Revert "travis: allow build on emacs-snapshot to fail"

This reverts commit 54c76b4cab6b862e11f229025d99a5f3ad1af6ec.
fix ff24d86