Upgrade haml-lint to v0.10.0
Remove the specific version from coveralls

Since we do not use the coveralls code directly we do not really need
to explicitly limit the gem.
Upgrade minitest to v5.5.0
Upgrade activerecord to v4.2.0
Upgrade redcarpet to v3.2.2
Add notes about gem upgrades to CHANGELOG
Merge pull request #96 from acant/gem_upgrades

Gem upgrades