Break apart JavaScript source into smaller modules

[timlindvall]

Now that we have grunt-include-replace integrated into our build step (#66), we should look into how we can restructure the /src/js directory to have individual components (HopscotchBubble, utils, Hopscotch, and other miscellaneous modules) belong to their own files, which are then concatenated during the build step using hopscotch.js as the include-replace template.

Currently, there's a few globals we rely on in the closure that's shared among components. As part of this, we might consider refactoring these into existing or new components.

[kate2753]

Work in progress can be found on branch GH-72. We are using babel and browserify and re-writing hopscotch in ES2015.

[kate2753]

Closing this ticket and will open more issues with specific tasks.