Add groups gallery. #27

Adds a groups listing and maps. Still needs a groups in your areas tab.
There is an issue on Line 63 of the groups controller where the code will randomly not work with the
error: uninitialized constant Group::GroupsController, yet some time later with no code change, it'll
just suddenly start working again.

The javascript could potentially be simplified to reduce the duplication, though would require a bit of refactoring.
Merge branch 'master' into groups-gallery
Bundle update.
Relax Devise constaint slightly, to pick up bug fixes in the 2.1 branch.
Remove spork, and use spring instead.

At last, there's a decent alternative to spork. To run tests quickly do
spring rspec spec
The second run will go faster. This is especially important when running
small numbers of tests, e.g.
spring rspec spec/models/issue_spec.rb
... since you won't be reloading the whole of rails each time.
Upgrade annotate.
Annotate.
Whitespace.
Fix routing of group#all_geometries, and give permission to guests to use it.

Perhaps this was the problem Shaun was running into - it certainly gives the same
error message. If I'm wrong, then we can get a stack trace blaming the indicated
line of code.
Add auto_link to description, and simple_format when shown on the webpage.
Make string translatable.
Refactor logic around showing group joining.

As previously written, if you weren't logged in, you were assumed
to be in the group!
Based on #273 show to logged out users.
Move pending string in translations, and adjust tests.
Fix faulty should_not have_content - always hard to spot these.
Remove new group button.

The permissions were broken, and it's quite an instrusive button for something
that people are rarely going to do.

Replaced with (translatable) text at the bottom of the page.
Link to the groups list from the groups box on the front page.
Merge branch 'groups-gallery' into staging
Fix translation changed on branch.
Fixup
Groups (via profiles) need forcing since they are otherwise not used yet.