Started to implement Signal Recovery SR7230 lock-in amplifier.
Implemented several more commands. Changes to SR7225 class to enhance consistency.
Add SR7230 to documentation.
Implemented "Internal Oscillator" commands.
Implemented "auxiliary input", "instrument identification" and "auto default and calibration" commands.
Implemented several more commands.
Implemented binary data transfer.
Fixed typo.
Enhanced buffer reading and definition.
Fixed wrong argument order in sr7230 "TADC" enum.
Fixed logger message in SignalRecovery protocol.
Added SR7230 to builtin table.
Added several more commands; Only Dual reference command group is missing.
 * Implemented dual reference mode commands.
 * Implemented take data triggered command
 * Made numpy a dependancy.
Fixed protocol assignement in SR7230.
The spinx spelling extension is now deactivated on readthedocs.
Mock out numpy so that autodoc builds.
Add `future` to requirements.
Removed print statement.
Readthedocs uses python2.7 so unittest.mock is not available.