Make gulp config more bettererer

The commits lay out pretty specifically what I did but here is the main divergent change:

deleted the plugins folder and got rid of that `_*.js` nonsense. If you want to use a third party dependency, you load it via bower and gulp automatically grabs and concats the `main` bower files. Are you a developer that doesn't know how to use a package manager? You guys are fine too. Just make your own `plugins` directory and it is automatically loaded via the `**/*.js` glob.

Also added an "images" task. It makes no sense to go through all this trouble to concat and minify files when you can save so much data over the wire by compressing images for free.
don't these need to be compiled in a certain order? i know i had issues in the past when trying to do something similar

https://github.com/twbs/bootstrap/blob/master/Gruntfile.js#L101-L112