v0.10.8 release notes (errbit#2650)

Bump version to v0.10.6

Add release notes for v0.10.5 (errbit#2167)

Release notes for 0.10.4 release (errbit#2040)

Bump Errbit version to 0.10.3

Release notes for v0.10.2 (errbit#1949)

Airbrake:

`.host` deprecated since 5.0.0.

Replace with `.error_host`.

Update (errbit#1890)

Prepare to release v0.9.0 (errbit#1466)

* Prepare to release v0.9.0
* Use dev flag to indicate dev/release versions