Update bundle, moving to Rails 4.1.

Rails picked up one of my core extensions, which is nice. The
trim_blobs gem doesn't work anymore, it's been removed and
replaced with Rails' default functionality to filter the logs.
Removed OJ, as multi_json has been pulled from Rails and it's
easier just to use the default gems. Flashes have string keys
rather than symbols now, which simplifies the flash partial a
bit. I think that's it.