Removed browserify dependency.
Removed browserify dependency.

This is an artifact of developing the browserify tests. Browserify
is not actually required here because grunt-browserify is the only
task that needs it and already has it as a dependency.

Related to commit c79ed458ed44ee05593fe00894740048a763ddf8.

jasco/jquery-powertip,stevenbenner/jquery-powertip,jasco/jquery-powertip,stevenbenner/jquery-powertip