Update fixtures

Add competition fixture data and repository fixtures

Creates a competition and some teams (with proper groups) in the dev
database. Also creates repositories for those teams.
Catch connection errors when the webserver can't reach the arena

Resolves #60
Add an arena user to the dev data
Add default competition images
Merge branch 'develop' of https://github.com/siggame/webserver into develop

Conflicts:
	webserver/fixtures/competition_dev_data.yaml