Adds goal streak, highest streak, and can_accept_goal to users, re-adds custom_challenge_ud to challenge_display, adds completed and completed_time to goals, adds boolean tests to all models, fixes basic challenge system functionality, and creates a basic goal system.
Merge pull request #94 from TrevorJin/goal-initialization

Adds goal streak, highest streak, and can_accept_goal to users, re-adds ...