Remove Wire.begin from begin. Remove getShutdown().

Wire.begin() in the begin function was overriding other I2C settings. This will cause some user's code to break if they don't have a Wire.begin in setup(). Examples and Hookup Guide have Wire.begin()s inserted appropriately so hopefully it won't catch any new users off guard.

getShutdown looks like it was never built out. Removed to get rid of 'missing return value' compilation warning.