Get rid of dependency on pyserial

[Mogball]

Repositories should not contain binaries and we don't need as much information as pyserial gives anyways. We just need to be able to iterate over ports and identify which are AVR ports for autodetection. We don't need to show that much info for each port.

[dhillondeep]

There do exist some libraries that do this. Code is a bit ugly and we need to add some wrapper code but this can be done. I will pick this up for 0.5.0