Show error on attempt to register with disabled self registration

This happens for normal registration as well as registration via omniauth.

This also changes the redirect to not go to / and go to signin_url instead.
Merge pull request #1145 from opf/fix/disabled_self_registration_error
Add changelog entry
Update pry-byebug and its dependencies

This fixes a bug when stepping with pry:
https://github.com/deivid-rodriguez/pry-byebug/issues/11
Remove guard as we don't use it
Remove pry-debugger as we don't support Ruby 1.9 any more
Merge pull request #1148 from opf/feature/clean_up_gemfile

Gemfile: Clean up some development dependencies
Bring back test-unit dependency to fix CI::Reporter issue

Broken in 9721cb95: test-unit was previously present by virtue of
being a guard-test dependency.

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge branch 'dev' into dev-angular

Signed-off-by: Alex Coles <alex@alexbcoles.com>

Conflicts:
	Gemfile.lock