Enhance Gulp dependency compilation

Gulp automatically grabs all of the dependencies listed as main files in
`bower.json` except for jQuery and modernizr

Deletes plugin directory, bad development pattern. Doesn't make sense
with the existence of `vendor` directory anyway.

Concat all of the js in the js directory except vendor and compiled
files
Adds `gulp images`

Lossless image optimization including pngcrush(1)