User - Standard - Requirement modeling

Some of the changes I made should sound familiar since we've already done similar stuff in LendingRound.
I added the User-Standard association and set @standards to user.standards.
As for the requirements in users#show I made almost the same commit before pulling one of yours and had to merge and resolve conflicts. I added a condition for showing standard.requirements only when there are any.
In order for specs to pass with the new associations I had to create a user factory and force the user belonging to the standard factories.