Adds 'production' command line argument for gulp and make (Bug 1507811)

Adds 'yargs' and 'gulp-if' to allow the css to be compiled with
expanded comments for easier debugging.

Gulp Usage:

Running 'gulp' will behave the same as before this patch.
Running 'gulp --production false' will compile the css with
debug comments in place.

Make Usage:

Running 'make css' will behave as before.
Running 'make css production=false' will compile the css with
debug comments in place.

behatnotneeded

Change-Id: I83fa35a9ac179b0419dc0160b58cac01b929734a
(cherry picked from commit 364c007a)