* Update Makefile.common from prometheus/prometheus.
* Switch from Cirrus to CircleCI.
* Add CHANGELOG.md and VERSION.
* Drop inline /vendor.
* Update references to old github URL.
* Update copyrights.
* Update Go version.
* Skip building on aix (undefined: syscall.Mkfifo)

Signed-off-by: SuperQ <superq@gmail.com>