Add ability to flag guarded attributes on create()
This is a non-API-breaking change. :)
Fix the association builders so that they handle protected attributes
correctly, while still setting the relationship keys correctly.
New test and two new test models to prove working fix.
(These tests fail without the associated fix)
Merge pull request #288 from onemightyroar/bug-fix-association-guarded-attributes

Bug Fix - Association Guarded Attributes