Fixed a broken i18n spec
Don't change i18n version of Ruby 1.8 spec
Pin i18n to 0.6.x in parallel specs.

This should fix the build on Ruby 1.8.7.
Revert "Don't change i18n version of Ruby 1.8 spec"

This reverts commit 7f940849bd0e3ffb1a48433b5d058e51b0d3ae0f.