Merge pull request #154 from creature/student-event-ux

Some copy changes for events.
sign up to receive an invitation is dup when
there are no events.

also move inside section.
Move some logic about available slots out of helper methods, and onto the Invitiation/Sessions models.
Push some more logic down to Invitations, rather than checking roles from the views.
Don't produce output from these Rake tasks if running in the test suite.
Shorter version of these if clauses.
Control output of rake tasks using test doubles rather than checking the Rails environment.
Merge pull request #155 from creature/refactoring

Move some model logic out of a presenter; tidy up test output.
Fix dead link to "How to be an effective teacher"
Merge pull request #156 from ForbesLindesay/patch-1

Fix dead link to "How to be an effective teacher"
Add counts for coach spots and attendee numbers, to make event admin easier.
Merge pull request #157 from creature/event-admin-tweaks

Add counts for coach spots and attendee numbers
Details of what each gem is used for, to help beginners to the project.
show waiting list, limit workshop RSVP to 3.5hrs before workshop begins
update dependencies
fix locale issue
update restriction time on changing rsvp and notification message
Merge pull request #158 from despo/fix-times

Fix workshop time
update attendances view
don’t display sponsor log on workshop admin listing