Use merge to find valid FundingRounds
Use merge to find valid Investments
Refactor InvestorsController to exclude invalid investors
Fix test that broke because of implementation knowledge
Merge branch '65759474_investors' into serializer_specs

Conflicts:
	app/serializers/v1/categories/category_serializer.rb
Use fundings association to get a Company's Investors
Remove whitespace
Refactor FundingRound
Refactor Company to use database

Creating ActiveRecord objects is **much** slower.
Update Company spec
Refactor CompanySerializer spec
Revert "Merge pull request #69 from cloudspace/63485236_migration_cleanup"

This reverts commit 689130f7f4ff7e367dd074a57261aa654d4108b0, reversing
changes made to 3e82c3e5017d60664503fbb9c33909f35d2aa3f9.