Revert "Merge pull request #9126 from mbarb0sa/bugfix/json-decoding-in-rails-3-0-stable"

This reverts commit 360af4eba60823c978bd5791d40f85c7c7739c80, reversing
changes made to f93d04677066b74ebb69f57028586126fc19228c.
Use mail 2.5