Catch SlipLib Exception Per #62

[kb1lqc]

This PR pulls in IT #62 which fixes an exception that was uncaught and found during Hardware In The Loop Testing.

• Adds an exception for sliplib.slip.ProtocolError to receive()
• Also adds in a few reminders for unit testing.

[coveralls]

Pull Request Test Coverage Report for Build 58

• 2 of 6 (33.33%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-2.8%) to 67.045%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
faradayio/faraday.py	2	6	33.33%
<!--	Total:	2	6	33.33%	-->

Totals
Change from base Build 48:	-2.8%
Covered Lines:	59
Relevant Lines:	88

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💛 - Coveralls