v5.1.0 - Updating props now properly changes tracking data

Before #60 by @tanhauhau changes to props on intermediate components would not be updated when descendent components fired off tracking events. They would instead use the values that they were initialized with. They now properly update as their props update.

This is a bit of an edge case, but the usage feels natural enough that it makes sense to fix. It should not affect any current semantics or API. Take a look at the test cases added as part of the PR ( #60 ) for an example.

Much thanks to @tanhauhau for finding and fixing this bug! 🎉