use i18n < 0.6.2 or > 0.6.2

Due to https://github.com/svenfuchs/i18n/issues/192
i18n 0.6.2 breaks ruby 1.8 compat
Merge pull request #93 from inertialbit/fix-ruby18-compat

use i18n < 0.6.2 or > 0.6.2