Revert "Revert "track and enforce user-agent""

This reverts commit 2227d0042f166659466b38a1f2db975b735f3638.
reduce metrics generated by UA tracker
Merge branch 'master' into rkh-track-user-agent

Conflicts:
	Gemfile.lock
Merge pull request #142 from travis-ci/rkh-track-user-agent

track and enforce user-agent