upgrading to Ruby 2.1 and Rails 4.0

Squashed commit of the following:

commit 6fbede85e5bea2eb2d8a8e8aa9e83d8a569451bb
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Mon Mar 10 19:24:03 2014 +0100

    [FIX CI] opening an order

commit 35dc8ccaec8de8f06e47ed4e4000d0b27ce16912
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Sat Mar 8 21:37:19 2014 +0100

    [FIX CI] borrow models list

commit a209d0116069d3f47959802c90614761e155d762
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Sat Mar 8 21:28:04 2014 +0100

    [FIX CI] selector

commit 2e28b2f8fa99e95743fe1f79ae66be7e69a3f409
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Sat Mar 8 21:21:12 2014 +0100

    [FIX CI] missing translation

commit aaaae2cccfebf14b1b3e8b3c31a10b1251441426
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Fri Mar 7 11:50:21 2014 +0100

    trying removing default_scope to see the CI results

commit d12a30e97a45cf679909c36e2a57eb31e1693133
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Fri Mar 7 09:28:07 2014 +0100

    upgrading to Rails 4: using code eager_load for tests

commit b057e3053323ec8727077101a90eea1f2992a037
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Fri Mar 7 09:18:48 2014 +0100

    [BUGFIX] missing argument for path generator

commit 34d8318c453c5aa2c37352beb45e8cef8ae1c5ae
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Fri Mar 7 09:01:04 2014 +0100

    upgrading to Rails 4: removing extra join in scope; fixing page scroll in tests

commit 6fe7e3dc382251b01c465549c5ca2ecde6ea31c1
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Fri Mar 7 00:50:01 2014 +0100

    upgrading to Rails 4: reverting joins where needed

commit 145d0dc3a6ffe3ae2ac8992aa69cb363c69a40eb
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Thu Mar 6 14:11:39 2014 +0100

    upgrading to Rails 4: workaround preventing redundant inner joins

commit e5af736fee85f11decb348a0ed8fc5d9b5c2d29c
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Thu Mar 6 13:30:58 2014 +0100

    upgrading to Rails 4: symbolized order queries

commit e6933c50fb8359466b256683c6f18a0873afbded
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Wed Mar 5 14:56:03 2014 +0100

    upgrading to Rails 4: overriding attribute_names because sql view

commit d850fcd809451b0d02d589b164f5a2c8406c932b
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Wed Mar 5 14:03:05 2014 +0100

    upgrading to Rails 4: fixing typo (order instead of where)

commit 2bdd781fc0317bfc8ec01fc66c4d666a5467c00a
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Wed Mar 5 13:59:33 2014 +0100

    upgrading to Rails 4: find_or_create_by_*; association procs; update_all

commit 4fd2d1da4a8ba025329bf14b41b94b9abeb7e94b
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Wed Mar 5 10:09:46 2014 +0100

    upgrading to Rails 4: removing attributes mass-assignment restriction; downgrade paperclip gem; upgrade acts-as-dag gem

commit 023bf7e9d51e3347c714a2b1be67d98778e37dab
Author: Ramón Cahenzli <rca@psy-q.ch>
Date:   Tue Mar 4 17:19:28 2014 +0100

    Changing execution to Ruby 2.1.0

commit 1f0adc330ea8d06bffdac52ea18996b56bebe58a
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Tue Mar 4 17:09:48 2014 +0100

    upgrading to Rails 4 (wip)

commit ea4767d2e1f6d020db08af823ad2f4db9698da1f
Author: Ramón Cahenzli <rca@psy-q.ch>
Date:   Tue Mar 4 11:53:04 2014 +0100

    Trying Domina on Ruby 2.1.0