This commit creates and an example test file for the baes58 package that
integrates nicely with Go's example tooling.
This allows the example output to be tested as a part of running the
normal Go tests to help ensure it doesn't get out of date with the code.
- Call out in README.md that this is modified base58 (it's not the same as
normal base58)
- Remove the blurb about test_coverage.txt since it is no longer needed
now that the repo now has coveralls integrated
- Rename base58_check[_test].go -> basecheck[_test].go. Since Go treats
_<ext> special in some cases like for tests and conditional OS and
architecture compilation, it's a good idea to avoid naming files with
them to ensure a new special meaning doesn't break builds in the future
