Added support for some kwargs in the FakeVISA instrument() function. Also implemented a FakeVISA call to Instrument.close() and some basic checks to match up messages with responses. Probably a much better solution will be needed in t he future
Added in tektronix funcgenerator code that was accidentally deleted when moving
Added docs for tektronix funcgens and scopes
Added list_visa_instruments to toplevel namespace
Initial support for NI DAQs
Implemented list_instruments() to list all connected instruments
Fixed sphinx theme on RTD