Merge branch 'release/0.1.5'
Drop backports dependency

The gem is not tested any more on 1.8 and the version has reached its
end of life any way. Fixes #45.
Merge pull request #46 from betelgeuse/drop_backports

Drop backports dependency
Check that message is present before trying to include it in the exception
Merge pull request #48 from okgrow/master

Check that message is present before including it in the exception
Merge commit '56c301e9c5511df447128cc3f193d7ce6abdb68d' into develop