Implemented IEC60488 protocol.
Updated core module to use the protocol.
Updated core test suite.
Updated tox.ini to use py.test.
Removed api documentation of test code.
Enhanced documentation of protocols. Implemented testing of SignalRecovery protocol.
Added mock dependancy to tox.ini
Implemented a new transport module.
Added a few more tests.
Fixed several bugs related to the new protocol layer.
Removed LockedTransport code.
 * Added debug level logging to protocol classes.
 * Added simple linux-gpib adapter.
Implemented new simulation mode.
Merge branch 'feature-protocol' into develop
This closes #142.

Conflicts:
	slave/core.py
	slave/lakeshore/ls370.py
	slave/srs/sr850.py