Update contributing docs, sign CLA after pull request.
Allow tick frequencies less than 1Hz.

Fixed #214 (the firmware part at least).
Revert "Don't wait as log for RN-42 to boot up; it's quick."

It's actually NOT quick.

Fixed #224.

This reverts commit 7981e1dbf7bc83fc0b0ac6f31de351e763b354c4.
Bump AT-commander to fail faster if RN-42 is offline.
Add watchdog timer to changelog after testing.
Merge branch 'next' into iso