bundle update

There is a know issue with installing eventmachine 0.12.10 on windows (with ruby 1.9.2 and mingw32) - solved by using version 1.0.0

Running ```bundle update``` also updates the version of a number of other gems, and adds the x86-mingw32 platform.

I also note that the Heroku gem is now depreciated, being replaced by the Heroku toolbelt, see [Upgrading to the Heroku Toolbelt](https://blog.heroku.com/archives/2012/10/15/upgrading-to-the-heroku-toolbelt/).

(this pull request replaces the earlier one that blocked my master branch)