Merge pull request prometheus#148 from prometheus/beorn7/release

Cut v0.7.0

Merge pull request prometheus#130 from prometheus/fabxc/cut

Cut 0.6.0.

Merge pull request prometheus#117 from prometheus/beorn7/release

Cut release 0.5.0.

Cut v0.4.0.

Merge pull request prometheus#94 from prometheus/release-0.3.2

Release client_golang 0.3.2.

Merge pull request prometheus#90 from prometheus/beorn7/release

Cut v0.3.1.

Merge pull request prometheus#88 from prometheus/beorn7/release

Cut release 0.3.0.

Release 0.2.0.

Merge pull request prometheus#63 from prometheus/beorn7/versioning

Introduce versioning and clean up the headers.