Log Message:
Update ruby-unf_ext to 0.0.7.1.

## 0.0.7.1 (2015-04-18)

- Windows fat binary gems no longer require libstd++ to
  run, which are statically linked.

- Add a fat binary gem for x64-mingw32 (64bit Windows).

- Windows fat binary gems now include binaries for Ruby up to 2.2.