Optionally email students on enroll/un-enroll actions
by instructor from enrollment tab in LMS.

Also, add a test for this behavior.

Added self to authors.

Conflicts:
	AUTHORS
	CHANGELOG.rst

Previously, multiple copies of the watchers started from the different
shells would run simultaneously, which left the possiblity of zombie
watchers, increased resource consumption, and incorrect results. This
fixes that problem by only starting a watcher if that same command isn't
already in the process list.

Fixes LMS-499

Use md5 checksumming to verify that we only write out xmodule asset
files whose contents differ from what we are about to write. This
minimizes thrashing of the other watchers.

Fixes LMS-452

xmodule-assets creates coffeescript files in the output directories. On
its next run, it used to delete the javascript files compiled from those
coffee files. Now it doesn't which should make coffee have to do less
work.

Fixes LMS-451

Using `ulimit -n` to set the limit much higher than the default of 256
in Darwin seems to avoid the `EMFILE` error that was plaguing our Mac
developers.

`rake install_prereqs` requires a minimal level of ruby and rake already
installed. If it doesn't exist, then print out a helpful message
indicating next steps.

Fixes JIRA LMS-203

And remove redundant but != date parsing methods. In process make
the general parsing function less lenient (don't default date nor
month)

And remove redundant but != date parsing methods. In process make
the general parsing function less lenient (don't default date nor
month)