Bumped version number to 0.1.0
Merge branch 'release-0.1'
Added generic connection classes to interface with usbtmc devices and linux-gpib.
Merged branch release-0.2.0
GpibDevice connection supports triggering. The iec060488.Trigger class tries to execute connection.trigger() before sending a *TRG command.
Fixed bug in GpibDevice; It used primary, secondary as keys for the locks instead of board, primary.
Merge branch 'feature-connection' into develop
Bumped version number to 0.2.1
removed second assignement to __version__.
Added missing program header prefix to Command.write function, when no datas are passed in.
Merge branch 'hotfix-program_header_prefix'
Fixed bug in Command.write.
Added context manager interface to TCPIPDevice, UsbtmcDevice and GpibDevice.
Bumped version number.
Added helper function to InstrumentBase, to ease writing in functions.
Fixed several bugs in cryomagnetics module.

Several bug fixes wered done:
 * Added limits to `Range.rate` Command, fixes #132.
 * The MPS4G class now forwards its config to the Shim and Range classes, fixes #133, fixes #134.
 * Correct format strings are now used for the MPS4G.lower_limit, MPS4G.upper_limit as well as Range.rate and Range.limit, fixes #135, fixes #136.
Merge branch 'hotfix-mps4g'
merged hotfix for mps4g.
Bumped version number to 0.2.3
Fixed wrong start value in Input enum of LS340.