Burn script now uses pylibftdi

I'm working to remove pyftdi from the HiSPARC III code.  That library
always seemed to behave a bit strangely and didn't prove to be very
robust.  However, now I know that pylibftdi is not perfect, either:

    1. Opening the HiSPARC III device on channel A (configuration) resets
       the Cyclone chip and the configuration is reset.  You cannot just
       check if the device needs configuration or is ready for operation.
       Pyftdi can do this.
    2. In ftdi_set_bitmode, you can select the output lines.  This doesn't
       seem to do anything and the output lines have to be selected
       manually by setting the low bits.  Pyftdi does not need to do this.

Oh well...
Fix imports of test script
Hardware class: use new FtdiChip

The new FtdiChip uses pylibftdi instead of pyftdi. The Hardware class
is used by the HiSPARC III code.
Removed unused code
Test interface_select
Moved ftdi_chip class and tests

They were part of muonlab, but are now used by all of pysparc.
Updated README
Merge branch 'hisparciii'