Added interrupt support for encoder.

This fixes the four click reading of the encoder. The encoder is now
correctly read every click. Also removed link to dropbox copy of library
(does not compile).
Change to direct channel contron.

This removes seek and replaces it with direct channel control. This is
the type of control I would expect from an analog radio/analog knob. I
find it is easier to find the station that I am looking for. Currently
steps 200kHz so works with US only.
Updated operation instructions.
Merge pull request #2 from sparkfun/EncoderFix

Encoder fix and channel change