test cases for pbft-core funcs

[arcolife]

Need to integrate with Travis CI / Jenkins.

A highly disrupted dev cycle led us to a dark dark place, one without test cases.

Need to push for *_test.go files, just like https://github.com/truechain/truechain-consensus-core/blob/devel/pbft/src/pbft-core/config/config_test.go

cc/ @samikshan @hixichen