Add support for writing byte arrays into dict from js
Add support for including a js file in the page

Pass --include-js=path/to/file.js to build.emcc.sh to include file.js
in the empebble page. This is useful for testing (e.g., add code that
constructs AppMessage dicts).
Added jsonification for bytestrings
Added rudimentary button support
Now support long presses
Properly initialize button handlers
Fill text rect with background (what the pebble does)
Merge pull request #5 from mwylde/master

Add initial button support