Merge pull request airbrake#749 from airbrake/release-6-1-1

Release v6.1.1

Merge pull request airbrake#742 from airbrake/release-6-1-0

Release v6.1.0

Merge pull request airbrake#730 from airbrake/release-6-1-0-rc-1

Release v6.1.0.rc.1

Merge pull request airbrake#700 from airbrake/release-6-0-0

Release v6.0.0

Merge pull request airbrake#693 from airbrake/release-5-8-1

Release v5.8.1

Merge pull request airbrake#689 from airbrake/release-5-8-0

Release v5.8.0

Merge pull request airbrake#687 from airbrake/release-5-8-0-rc-3

Release v5.8.0.rc.3

Merge pull request airbrake#682 from airbrake/release-5-8-0-rc-2

Release v5.8.0.rc.2

Merge pull request airbrake#680 from airbrake/release-5-8-0-rc-1

Release v5.8.0.rc.1

Merge pull request airbrake#667 from airbrake/release-5-7-1

Release v5.7.1