Replace CoffeeScript logo with official version
Update README wrt CoffeeScript logo

The logo is no longer a recreation, but the official logo as provided
by @jashkenas.
Add alternative versions of CoffeeScript logo

Color, knockout, no-whitespace, color-no-whitespace, and
knockout-no-whitespace versions are included in this commit.
Changes CoffeeScript filenames, removes groups
Updates README to use production links to the SVGs
Merge branch 'pedromaltez-pm/patch/official_coffeescript_logo'