Add has_many :through associations
Speed up CategorySerializer#investor_ids by using new has_many associations
Add delegate method to Category
Refactor CategorySerializer spec
Rubocop style fixes
Remove specs for deleted method
Move `has_many :investments` into Investor concern
Rename a few tests
Optimize InvestorSerializer with new funded_companies association
Refactor InvestorSerializer spec
Refactor CategorySerializer to avoid awkward polymorphic.
Refactor NestedFundingRoundSerializer
Use FactoryGirl to build a investor company
Refactor NestedFundingRoundSerializer spec