add method to apply tinyify to a separate browserify pipeline, closes #1

[goto-bus-stop]

a take on #1

This would be used programmatically as

b.plugin(tinyify)
b.on('factor.pipeline', function (file, pipeline) {
  tinyify.applyToPipeline(pipeline, b._options)
})
b.plugin(factorBundle, { /* opts */ })

and would flatten and minify the pipeline.