Upgrade lineman for plugin support

(required me to make the webfont config compatible)
Remove bower, since that seems superfluous
Configure the grunt task instead of using .bowerrc

This will let us extract more behavior into the plugin, which will make
life easier for users. It has the happy side effect of producing nicer
output.
Add a bower target to clean

Now when `lineman clean` gets run, the bower dir is also deleted.
Plugin-ified all the things

Now receives its Bower configuration from the 
lineman-bower module in npm.

Had to take two steps at once because user config
was knocking out the array-based properties being
set by the plugin (this is a new issue with how
plugins will relate to user overrides that I hadn't
considered).

Solved it by extracting all the other config out
into local plugins as well.
Merge pull request #28 from searls/bower-plugin

Bower plugin