Bump 0.6.4

Folks are having trouble with activesupport 5 beta. This release should
prevent mailcatcher attempting to use the beta gem.

Bump 0.6.3

Bump version

Let's see if bumping eventmachine solves the memory leak issues.

Bump 0.6.1

Bump 0.6.0

Bump 0.5.12

Bump 0.5.11

Version v0.5.10

Release v0.5.9

Bump v0.5.8