fix(keywords): gulpfriendly instead of gulpplugin

Fixes #1. This is not really a `gulplugin`, see guidelines:
»Other libraries that are not file manipulating
through streams but are made for use with
gulp are tagged with the gulpfriendly keyword on npm.«
chore(engines): make sure to have caret (^) deps support
chore(release): prepare v0.0.3