Add tournament model and relationships
Merge branch 'develop' into feature/tournament
Define API namespace
Support only single & double round-robin tournaments for now
Discard new & edit routes on API routes
Add has_key? to Enumerable
Allow creating tournaments with known type and a certain number of participants
Generate matches when creating single or double round-robin tournaments
Add final matches
Merge branch 'feature/tournament' into develop
Merge branch 'develop' into feature/match
Add round number to matches
Merge branch 'feature/match' into develop