Reinitialize bundles automatically in the event of a compile failure

This pull request addresses [issue #355](https://github.com/andrewdavey/cassette/issues/355)

If a compiler, such as SASS or Less or Compass had a compile error previously the error would become "stuck" in the AppDomain and no further attempts to rebuild the bundle would be made until the AppDomain recycled.

That's less than optimal if you tweak the file to fix it and Cassette says it's not fixed.

This changes the code to re-initialize the bundle once if an exception occurred during the initial rebuilding, which allows compile errors to be reevaluated without a rebuild.