v0.7.0

Changed

• PMM-3512: Switched to kingpin library.
  This is a BREAKING CHANGE because kingpin uses -- instead of - for long flags, so be careful when updating.
• PMM-2261 Unify common mongod and mongos server metrics, thx @bz2
  This is a BREAKING CHANGE. The labels of these metrics are now prefixed with just mongodb_ rather than mongodb_mongo[ds]_.

Added

• Fine grained error handling for index usage and collection stats (#128), thx @akira-kurogane
• Introduce a docker go build that creates a mongodb_exporter binary within a container (#112), thx @mminks
• Ability to make releases and snapshots with GoReleaser