Move serialTestClass over to faradayio module

[kb1lqc]

Per https://github.com/kb1lqc/faradayio/tree/serialtest move the SerialTestClass over to the main faradayio module. This function is useful in everyday use of the faradayio module.

• Implement SerialTestClass in faraday.py
• Move unit tests over to use faradayio version of SerialTestClass

[kb1lqc]

Per https://travis-ci.org/kb1lqc/faradayio/builds/346678195 the serialtestclass.py dependency in the code has been removed. This is in:

https://github.com/kb1lqc/faradayio/tree/serialTestClass

[kb1lqc]

Completed with #46!