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 'performance'
Merge branch 'performance'
Ignore the resque-web url file.
Use the built-in formtastic label translations, rather than hardcoding a label.
Update subdomain test and leave an explanatory message in the validator.
Fix broken tests.
Merge branch 'master' into groups-gallery
Add e-mail addreses (clickable) to membership management pages; fixes #220
Make e-mail links clickable
Pin devise due to failing tests on 3.0.0
Bundle update
Don't use stub! and mock, they are now deprecated. stub and double are the replacements.
Newline handling has changed slightly in new versions of mail. Update tests accordingly.
Check for name and email before inviting user.

The behaviour of mail has changed, and now throws an error if there's no To: on
the mail. Previously when submitting a blank invite form, we'd try inviting
email: "" and it would silently do nothing, and then the user would be invalid and
the form re-shown.

There's probably a better approach, but an additional benefit here is clarifying which
values we're checking, and which actions are being made, rather than just having everything
as one concatenated statement.
Add a check for encoded subject lines.

Problem was fixed in 'mail' gem somewhere between 2.4.4 and 2.5.4

Refs #226
Remove stray entries from Gemfile.lock
Merge branch 'staging'
Patch to possibly add threading headers to cyclestreets mails

include a References header to be the same as the reply_to address, which is a valid email address for that thread. Will do basic threading.

Ideally the message ID would be populated here, and would take the message-in-thread-number that comes in far higher up in the call change, and do <msg-number>-<threadid>@domain so we get predictable msgids, and can then add the References programatically.
Improve layout and wording on group admin page.