Added new secret_key_base config parameter to initializers.

This is a new Rails4 config option that, if present, encripts the client-side cookie store to make it unreadable as well as tamper-proof.

It has been changed in the initializer file used for Travis CI, which is present in git, but also in the initializer files used in real environments, which are not in git.
Removed log4r gem because of incompatibilities with Rails 4.

This means going back to the default Rails logging.

The incompatibility is caused because Rails added a new "formatter" method that logging frameworks must implement. Log4r does not implement it; when trying to start a Rails 4 app using log4r logging, an "undefined method 'formatter'" error is raised and the startup fails. Highest criticality!

It seems logging frameworks (yell, log4r) have not adapted yet despite Rails 4 being released a month and half ago (and RCs long before that). There's a pull request in the log4r github repo supposedly fixing this that has received no attention for a month. I suppose people are happy enough with Rails logging, because obviously logging frameworks are not getting enough love. I'm really sorry, log4r is very nice, but I just can't hold migrating to Rails 4 because of this, and I've lost confidence in log4r devs adapting to the state of the art. Back to the default logger it is.