added verbosity to test helper

Fix example text in README and union_test.go

more idiomatic Go error handling

better support Windows zero-time without loss in granulatiry due to i…

…nt64 overflow

library declared as v2 module; updating docs and examples

go modules

test files are in goavro package rather than goavro_test

updated dependencies and copyright notices

updated dependencies and copyright notices

several bug fixes