Update tests to use integer values for encoding

[drinckes]

Update the tests for each implementation to use the integer coordinates in the encoding test data and the integer encoding function.

Should also add a test to confirm that the conversion from degrees to integer is within expectations.

[drinckes]

It turns out everything can play nicely with floats in the test data, so this is no longer necessary.

[drinckes]

As per the comment in #716 (comment), once I add tests that confirm a code's bounding box contains the original coordinates I get failures. It doesn't matter whether I use Round() or Floor() in the conversion from float to integer, because the issue is with the accuracy of the float representation.

So I thought I wasn't going to have to do all this but it looks as though I will.