reverse boolean on authorized key remove

When we remove a key, we should only delete
the specific key and not every other key.
Merge pull request #567 from ontohub/fix_nasty_authorized_keys_error

Reverse boolean on authorized key remove. Should fix #559.
Disallowed diff views in robots.txt

concerns #440
Fixed paths for git_daemon

related to #559
display_commit more robust

Don't raise an exception if the revision can not be determined.
Upgrade to Devise 3

solves #564
Merge branch 'staging' into develop