Implementation of toEthAddress

[vonum]

Test for fil address lib:

1. toEthAddress
2. fromEthAddress

Refactored toEthAddress implementation.

[scotthconner]

I'm seeing fuzzing, but I still don't see legit existing cases of f1,f2, etc. For instance, where are the tests that take a hard coded value (an f0 or f1 address), that is actually not fuzzed, and legitimately tests it for a specific output?

[vaniiiii]

Moved to #23