add support for USB PowerLinc

- bump to 0.4.1
- require serialport ~1.1.0
- update Readme.md

NB: my insteon hub, my smartlinc, and my powerlinc all got factory reset "one too many"times. during my first test pass, everything worked on the smartlinc and powerlinc. after no changes to the code, but a couple of factory resets, the extended responses no longer come through. **please** try this on your hub or powerlilnc before a final commit to verify that it's working for you. i'm going to buy a new hub so i can continue to test...