* Consolidation of Makefile and Makefile.release

Several changes:
1. All go specific target like `go generate`, etc. has
been moved to Makefile. Now Makefile.release does not
repeat go build, etc. related rules.
2. In Makefile.release, the binary build is done through
`docker run` and with a fixed specific go version (currently 1.8.3).
This will help making sure build process could be reproduced
on any dev platform, with no dependency to the golang version
installed on the platform.
3. Platform related flags (e.g., "GOOS=darwin") are passed through
Makefile (not Makefile.release).
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Update to only use `make` without running inside `docker run`
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>