Update Bower to 1.2.8 and upstream to v85

Update Bower to 1.2.8 and upstream code to v85.

```
Bugfixes:

* Any errors in a Rakefile will now be explicitly shown as such instead of hidden in a assets:precompile task detection failure (#171)
* Now using correct default "hobby" database #179
```

* [heroku-buildpack-ruby/CHANGELOG.md at 55ff6dd8e845f54943f4083185e009f1d0a144a5 · heroku/heroku-buildpack-ruby](https://github.com/heroku/heroku-buildpack-ruby/blob/55ff6dd8e845f54943f4083185e009f1d0a144a5/CHANGELOG.md#v85-12052013)