* Update go to 1.7.4 and 1.6.4 to fix security issues
The go team recently rolled out two releases to address security
issues. Details available on the [go release
site](https://golang.org/doc/devel/release.html).
This commit updates our explicitly supported versions.
It also includes a comment about two CentOS requirements (enable
user_namespace and ensure that the static c library is installed) that
are required for the pacakges to pass their tests.
* Flake8 cleanup
f0dcb5bbf7