Remove unused positions.
Add rspec binstub.
Make a new version of an issue when a thesis is added to or removed from
it. Show the correct version of each of an issue's theses on its version
page. When reverting an issue, revert each of its theses to the proper
version too.
Reverting a thesis should create a new version of its issue.
Merge branch 'develop' of github.com:TheFuturistParty/debate into develop