Add removeDevice and device.remove(), tests, and improved test configuration

With this pull request I've implemented the removeDevice() and device.remove() functionality in the Loggly API and I have implemented tests that verify their functionality.

I also made a modification to the test-config.json file format which explicitly sets the Loggly input names used in the test.  We already had an input named 'test' in our Loggly account which the tests were trying to use, rather than the inputs we created _for_ testing this library.

Now developers must specify the input names along with the ID and token in test-config.json.

Feedback welcome.