Made some Threading changes
	* StreamWriter expeects a Conditon variable to be passed in
	* Various objects that create StreamWriters expect to be
		given Condition objects
	* s3g.from_filename needs a condition object
	* MachineFactory.build_from_port has a kwarg option for Conditions,
		but will create one if not specified.
	* Buffer overflows are not caught, but are expected to be caught
		by an object build on the driver
	* StreamWriter no longer waits on a buffer overflow
Updated unit tests to reflect refactor.
added relevant changes to examples
Merge branch 'master' of github.com:makerbot/s3g into stream_writer

Conflicts:
	tests/pi_test_MachineFactory.py
Updated Parser
	* Parser now only transitions state if the command is successful
	* Gave point class a copy function
	* Created new NoFeedrateSpecifiedError
Merge branch 'stream_writer' of github.com:makerbot/s3g into stream_writer
Edited set_external_stop
	* Abstract writer's set_external_stop now takes a kwarg value, which
		the external stop will be set to
	* GcodeProcessors changed to be similar
Merge branch 'stream_Writer'

Conflicts:
	makerbot_driver/Gcode/Parser.py
	tests/pi_test_MachineFactory.py
Updated unit tests for threading.Conditions