upgrading to Rails 4.0.4, upgrading gems and fixing ci

Squashed commit of the following:

commit a6749d983cd5ddcaf96b953b60c08d0a2cab74f8
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Wed Apr 2 12:24:54 2014 +0200

    [FIX CI]

commit 8e975bba8ed0c25d6e89c51dd7b7f69f8a228ad6
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Tue Apr 1 16:54:09 2014 +0200

    [FIX CI] capybara dom

commit d753fe6a80dc8915975219539762e3ba64b8ddfa
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Tue Apr 1 16:49:26 2014 +0200

    [FIX CI] jump to the next availability change date

commit 3a5b6f86afa86ba414057f2d2726aae190cbb6d2
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Tue Apr 1 14:43:40 2014 +0200

    downgrade font-awesome-rails gem and removing thin gem

commit 482086dfb19e790ad51eedb5399aae308ed57ec3
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Mon Mar 31 18:39:36 2014 +0200

    downgrade jquery-rails gem

commit d3e74d5cfae2284cefdc82fad1e79e2991cc4c17
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Mon Mar 31 18:31:47 2014 +0200

    removing deprecation warning

commit ce99fabd9fb8117d2eb91263f8aac3d358bd76a0
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Mon Mar 31 18:21:15 2014 +0200

    downgrade jquery-rails gem

commit fcccfc2a55887ada9ecbc45fe1f67dfde5e558eb
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Mon Mar 31 18:13:34 2014 +0200

    downgrade paperclip gem

commit 15f904f469a9473770d76adbdea5c85387b0f5a3
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Mon Mar 31 18:03:14 2014 +0200

    upgrading to Rails 4.0.4 and upgrading gems