Release v1.2.3

1. Bug fixes on EventThreadSafe
2. Add UT coverage and fix golint issues.

Update license to apache 2.0

v1.2.2

Update license related comments to apache 2.0

Make repo public

v1.2.1

Update license section in readme

Bump up to stable version of v1.2.0 for all RK series.

Updating contribution guides

v1.0.9

MaxSize in default LumberjackConfig should be 1024MB

v1.0.8

[rk-logger] Create ZapConfigWrap structure in order to overcome level…

v1.0.7

[rk-logger] Add utility functions [commit:dongxuny]

v1.0.6

[rk-logger] use stdout as default output path for stdLogger [commit:d…

v1.0.5

[rk-logger] Add Standard logger config as variable [commit:dongxuny]

v1.0.4

[rk-logger] Add noop logger [commit:dongxuny]