Fix various coding weidness discovered during the Checkmate review

[jon-betts]

Via 3 was used as the base for Checkmate and during that review a number of weird things were discovered:

• The routing should be moved to route.py instead of being in the views.
• The requirements.in files should not have any version numbers
• The status end-point can use much simpler ways of returning a nice response
• We should import view_decorator directly instead of the module