Callbacks for All

This updates the project to have callbacks on all commands as well as the following changes:

• Based on feedback from #12, the packets are now guaranteed to be sent in the correct order.
• All parameters of the methods are validated to ensure they are in the proper ranges.
• Two new methods were added: channelOff and channelOn. In addition, these methods are also called automatically when a duty cycle or pulse length is too small or large.

TypeScript 2.0 and @types

This updates the code to pass with TypeScript 2.0 strictNullChecks. In addition, it switches from tpyings to @types for the debug and i2c-bus typings. Since the interface of debug is different from the two typings sources, I have bumped to major version just in case.