Security fix

Hey guys, this is a small security change for the project. Having the secret_key public puts any deployed instance of this project on risk. To generate a new key, just run:
 
$ rake secret

Add the new key to a new environment variable named **SECRET_TOKEN**
If using heroku:

heroku config:set **SECRET_KEY**=new_key_here

In case the env. var isn't defined in the system, it will fallback to the previous one so that anyone contributing to the project don't have to generate a new key every time they do a fork. Cheers!