Caching of raw info values.
Fixed #+ method so it only affects the last argument
Merge pull request #259 from nandinga/raw-info-caching

Caching of raw info values.
Merge pull request #258 from nandinga/fix-plus-modifier

Fixed #+ method so it only affects the last argument
Add ability to silence errors more elegantly

Fixes #257
Refactor MiniMagick::Tool::OptionMethods
Remove JRuby and MRI 1.9.2 from Travis

* We remove JRuby because the "open3" library doesn't work on it.
* We remove MRI 1.9.2 because it's already end of life.