Update to rails 4.1

I noticed the PR from @chunlea and used parts of his code to upgrade huginn to rails 4.1

Here what is done so far:

* Update rails and the most essential gems
* Used a fresh rails 4.1 app as boilerplate to update the environment configurations
* Updated the devise initializer based on a fresh installation
* Tests pass
* The application boots and seems to work with no problems

What still needs to be done, or discussed:
- [x] Further check for gem updates and test them (Gemnasium?)
- [x] Verify everything runs in production
- [x] Verify the twitter-stream actually works
- [x] Check the geokit related agents (did update geokit-rails but not geokit, which currently is two minor versions behind)
- [x] Update the staging environment configuration (left it as it was because it looked out of dated compared to the 3.2 production environment)
- [x]  Decide whether or not to migrate to strong parameters (would be some work but should pay off in future updates)
- [x] Test updating `rturk` and `twillo` (@cantino will do this)

~~The only thing needed to be done manually to update is to set the `DEVISE_SECRET_TOKEN` in `.env`~~