Upgrading domina (port management, timeout ...); using RUBY_VERSION env-var

Squashed commit of the following:

commit 92ea812b6372a38deec78e9faab27326e9459448
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 13:16:37 2013 +0100

    fix

commit da054d632136b83869abbcc740e0e0f766745e3c
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 13:15:41 2013 +0100

    Revert "Switching from firefox to chrome"

    This reverts commit 5b8680498558c171a537d402f58173a7bb61617c.

commit 1f5b2499884b52b24fcc9679b090cdda2b5c5dda
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 13:15:25 2013 +0100

    Revert "Updated selenium webdriver"

    This reverts commit 7de1718a551f1b156c6c69aade114cd736b89528.

commit 7de1718a551f1b156c6c69aade114cd736b89528
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 13:04:57 2013 +0100

    Updated selenium webdriver

commit 5b8680498558c171a537d402f58173a7bb61617c
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 12:42:52 2013 +0100

    Switching from firefox to chrome

commit 1b03e44f2cf5194b8e59a2980b7f22b72879b6b8
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 11:13:11 2013 +0100

    fix

commit c1137fe35adf0427120286ee6a09eed07ecb3544
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 10:28:49 2013 +0100

    Domina: define ruby version as env_var; increase timeout for bundler

commit 24ee08ddbf83f8d038ee82a522cddb47c9f371ed
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 2 10:08:53 2013 +0100

    Domina: using the ports feature for getting a xvnc port
Switching from chrome to firefox in some cases for more stable tests
Domina specification: features are now ordered before specs so they will be executed first
Fix close modal icon missing. Cleanup combos documentation.
Styleguide: document new tag cloud variations.
Furtherly tweak tag cloud button spacing.
Fix type of toolbar header.
Add bottom spacing to User Groups in the /my/ dashboard.
Styleguide: document new tag cloud variations.
Quickfix a failed rebase (legacy colour variables used in the tag cloud module).
Consolidate line-height values.
Fix buttons stand-alone icon separator colour.
Optimize thumbnail container box model.
Optimize thumbnail container box model in clipboard.
Optimize thumbnail container box model in the dashboard.
Introduce .context-fix for .ui-resources-holder paddings.
Fix close modal icon missing. Cleanup combos documentation.
Styleguide: document new tag cloud variations.
Styleguide: document new tag cloud variations.
Optimize thumbnail container box model.