fontify most magit `with' and `define' macros

In libraries that are part of Magit automatically add font-lock
keywords for macros like `magit-define-command' and
`magit-with-section'.  This can be turned off by setting
`magit-add-font-lock-keywords' to nil.
sanitize tests/run-tests.el

* don't use defvar when let is enough
* use built-in functions to create paths
* test whether dirs exist before adding to load-path
tests/run-tests.el: add /path/to/magit/../{mocker,cl-lib} to load-path

It is quite reasonable to expect the directories containing the
dependencies to be located in the same directory as the magit
directory is located in.  At least this is the case when manually
installing each package as a subdirectory of some "site-lisp"
directory.  Or when using submodules as I do.
Makefile: reduce output

Use the intended emacs command-line options instead of using
--eval FORM when the latter is not actually necessary.  When
it is necessary "pretty-print" FORM.
quiet byte-compiler
Fix bug where the wrong author info is used for committing

The author information is saved in the buffer-local variable 'process-environment' in
the log-edit buffer.
To reset its value, kill-local-variable must be called not after, but BEFORE
switching away from the log-edit buffer.

Otherwise, the old author information will be reapplied in the next commit that uses
the same log-edit buffer.
Merge pull request #643 from tarsius/quiet

quiet byte-compiler and make
Merge pull request #642 from tarsius/tests

tests/run-tests.el: add /path/to/magit/../{mocker,cl-lib} to load-path
do not activate magit specific font-lock keywords

We haven't decided yet how to best activate these keywords.
So for now users have to activate manually in all elisp files:

    (font-lock-add-keywords 'emacs-lisp-mode
                            magit-font-lock-keywords))
Merge branch 'font-lock-keywords' into next
Merge branch 'maint' of git://github.com/nonsequitur/magit into maint
Merge branch 'maint'
Merge branch 'master' into next
magit-simple-keys.el: fix typo in commentary
magit-classic-theme.el: add library header
Merge branch 'cleanup'
Merge branch 'master' into next
README.md: put extensions in own section, push it down
README.md: link to up-to-date contributors list on github

Also prettify link to the owners team.
README.md: fix links