Freshroastsr700

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Resolves feature request documented in issue 31
freshroastsr700 object can now be instantiated with manual control
of the software-based heater algorithm. Tested in Ubuntu 16.04.

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Resolves issues 22, 23, 24 and 25, and 29 (the latter introduced by
0.2.2). Added logic to handle hardware
connects and hardware disconnects properly in all supported OSes. Software
now supports multiple connect()-disconnect() cycles using the same
freshroastsrs700 object instance. Tested in Windows 10 64-bit and
Ubuntu 14.04.

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[Introduced issue 29. Inoperable in Windows environments - do not use.]

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Resolves issue 20 by managing hardware discovery logic in the
comm process, eliminating the need for the thread heretofore
associated with auto_connect. Openroast 1.2 (currently in development)
now operates properly in Windows 10 64-bit, with this fix.

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Completely rewritten PID control for tighter tracking against target temperature (when freshroastsr700 is instantiated with thremostat=True).
Callback functions for update_data_func and state_transition_func now called from a thread belonging to the process that instantiated freshroastsr700. This was necessary for Openroast version 1.2 code refactoring.
Reduced processor load for PID control as part of code refactoring.

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Added support for python 2.7.