Add Bower tasks to build task

[juandopazo]

grunt build should call bower install before yogi build and the rest of the build process.

[ericf]

@juandopazo why are you removing the bower_components dir? Can't we simply leave that there?

[juandopazo]

I thought it would make sense to clean up after ourselves, mostly because I don{t know all the details of what happens after a build.

[ericf]

This would be like going in and removing the node_modules/ directory. I think we should leave it because then bower ls shows which version of Pure we're using. And in the future—whenever we get rid of the build/ dir—we'll need the bower_components/ dir there because it would be used every time a developer builds.

[juandopazo]

Ok. Rolling back then!

[ericf]

@juandopazo You want to keep ypromise out of YUI's src/ dir, correct? If so go ahead and merge + release this — I gave you push access to this repo and publish access to the npm package.

[juandopazo]

I may have to do more than that, since ypromise contains YUIDoc information.