Split encoding functions to expose integer encoding for tests

[drinckes]

The encoding function takes two floats (latitude and longitude), converts to integers and then does the encoding. Due to language, platform and/or os implementations, the initial conversion from float to integer can differ slightly.

To enable consistent tests, we want to make the integer encoding a separate function that can be called by the tests.

It should be called something like encodeIntegers, and take as arguments the latitude multiplied by 2.5e7 and longitude multiplied by 8.192e6 (the precision of the longest permissable codes).

This needs to be done for each implementation.