gosrc: Remove noise packages.

A package will be removed if either it has no commits in two years and
no imports from other packages, or it is created for a quick bug fix,
which means it has one or two commits within a week of creation time and
no other activity since then.

This CL checks such packages from GitHub and BitBucket utilizing their
API to gather commits information.

This CL also removes the checks for references for GitHub repo, instead
it check the most recent commit from default branch.

This fixes #405

Change-Id: I14b0f0133f31851511aaa63eee8acbfba63e13d2
Reviewed-on: https://go-review.googlesource.com/24513
Reviewed-by: Alan Donovan <adonovan@google.com>
11 files changed