lib: Add CommonJS/browserify support
lib: Add CommonJS/browserify support

Add CommonJS support so that Dropkick can be `require`'ed.

chrismoulton/DropKick,alexgleason/DropKick,acebalajadia/DropKick,alex-riabenko/DropKick,Robdel12/DropKick,alexgleason/DropKick,alex-riabenko/DropKick,chrismoulton/DropKick,acebalajadia/DropKick,GerHobbelt/DropKick,GerHobbelt/DropKick,Robdel12/DropKick