Adds documentation around pwm and removes documentation around the buggy DAC
Adds documentation about how to output a pwm signal
Removes net.connection from not implemented list
Removes sleep from API docs
Fixes pwmDutyCycle function name and removes mention of default frequency
Fix setPWMFrequency -> pwmFrequency
Merge pull request #13 from tessel/jon-api-update

PWM/DAC API Update