Allow users editing their membership dates.

But do not allow to change their status.
Add ability spec
Add test for group memberships set into the future
Repair SimpleCov and add your_platform to scanned classes.
Merge pull request #38 from fiedl/jr/repair_simplecov

Repair SimpleCov and add your_platform to scanned classes.
update to ruby version 2.1.1.

for details, how to adopt your local development machine,
please see the trello card:
https://trello.com/c/o3rC95dK/598-update-auf-ruby-2-1-1
csv: adding list for member development of a group, i.e. when did status changes occur.
moving Corporation#leaf_groups to Group#leaf_groups.

This generic method makes also sense for groups.

In particular, I’m going to need this for the csv export of status
membership developments for any group.
Improving Group#member_development_to_csv.

* Making it more efficient.
* Making it generic: It now works for any Group not just for
Corporations.
css: extracting font specifications of wingolf layout into one single file.

This way, the font should be easier to adjust.

Trello: https://trello.com/c/5k6dOXFA/600-font-schaltstelle-einrichten
UserVoice: https://wingolf.uservoice.com/forums/237354-allgemein/suggestions/5637826-schriftart
css: making the font slightly larger.
security fix for CVE-2014-0130.

trello: https://trello.com/c/0TcN1TSF/602-security-cve-2014-0130.

further reference: https://groups.google.com/forum/\#\!topic/rubyonrails-security/NkKc7vTW70o
updating devise due to security issue '2014-05-07 CSRF TOKEN FIXATION ATTACKS'.
update to ruby version 2.1.2.

release info: https://www.ruby-lang.org/en/news/2014/05/09/ruby-2-1-2-is-released/
trello: https://trello.com/c/PySEkLOD/615-update-auf-ruby-2-1-2
replacing rmagick gem by mini_magick gem.

* https://github.com/carrierwaveuploader/carrierwave\#adding-versions
* https://trello.com/c/dQn0NeXp/616-rmagick-minimagick
fixing AttachmentUploader#cover filter.
fixing workflow_kit gem to version 0.0.7 until migrating to rails 4.

workflow_kit 0.0.8 only supports rails 4.
adding newrelic service.

website: http://newrelic.com/ruby
trello: https://trello.com/c/BVddSI1g/585-newrelic
newrelic: fixing configuration to import license key properly.
urls: adding the title to the url for Pages, Groups and Users.

railscast: http://railscasts.com/episodes/314-pretty-urls-with-friendlyid\?view\=asciicast