Merged the BundlerPlugin and BundleSourcePlugin interfaces, relying
instead on the composite pattern to allow a single js bundler that can
act as the front-end for all 'text/javascript' bundlers.
Renamed some classes so they more accurately described what they do.
Squished a number of the easy TODOs.
Merge branch 'bundler-exploration' of github.com:BladeRunnerJS/brjs into bundler-exploration