Updates for new font name. Was FONT_KEY_GOTHAM_34_MEDIUM_NUMBERS and is now called FONT_KEY_BITHAM_34_MEDIUM_NUMBERS
Fixes building with 32-character secrets (like Google) Fixes https://github.com/IEF/authenticator/issues/11
Updates README with a few more steps I had to do to get this installed. First time building a Pebble app so hopefully it helps someone else too.