bump rails to 3.2.13
fix `invalid byte sequence in US-ASCII` error.

Error got ruby(1.9) and rails(3.2.13) and i18n-js(2.1.2). Use i18n-js HEAD.
refs. https://github.com/fnando/i18n-js/issues/137
Merge pull request #108 from onk/bump_rails_to_3_2_13

bump rails to 3.2.13