explicitly state the format of the template

Hi,
this pull request includes one important fix and two minor ones:
1. State the format explicitly when rendering the error-partial. The reason is that I was getting errors when a route with a format was accessed, such as "http://www.domain.tld/stylesheets/base.css". Rails was complaining that there was no view with an css extension it could render.
2. I relaxed the bundler requirement as I'm using bundler 1.1.rc
3. I took the hardcoded string for the errship_standard and make it i18n.