add wiredep support.

I'm a noob with gulp and all this fancy stuff.

I released wiredep 1.1.0 with stream (?) support: https://github.com/stephenplusplus/wiredep/commit/37b9850088a9ecbb86e2cefb6232ac4e8707469a

I tested this, and it works. So, please, smart people test now :)

It sets up a watch on `bower_components`, so that any time you install a package, it will run wiredep. Works nicely!

It also uses the name `wiredep`, as opposed to `bowerInstall`. So, it's `gulp wiredep`.