RFduino firmware: advertise as non-connectable peripheral

RFduino Arduino library v2.2 supports non-connectable advertisements - relevant commit: https://github.com/RFduino/RFduino/commit/24c9bac899c51563eac324fd62437862f71f080b

This pull request uses this new feature to make the RFduino advertise as non-connectable.

Previously, a device could connect to the RFduino, which would disable advertising. Making device non-connectable ensures that it will advertise as expected.