Rename "children_must_be_valid" function

"Children" implies something incorrect especially as we get into
compound objects
Update rspec

Uses latest 2.x which seems to fix some odd errors when trying to run
bundler with rspec 1.3.x
Move destroy-related functions into form backer

Makes it easier for apps to have their own FBOs
Merge pull request #1 from OregonDigital/feature/better-api

Feature/better api