* GH-453 Check for changes in device metrics before sending Event.
* Implement and test new equality for ScreenMetrics
* Implement IEquatable
* Make Screen Metrics Readonly :) add more tests
* Update docs
* Condense tests into single Theory
This tests equals/not equals in one test and allows us to add more inline data cases.
* Additional optimizations
* More Changes for tests
* Optimize code even further and fix up tests
James Montemagno