Convert ActiveModel to 1.9 hash syntax.

I also attempted to fix other styleguide violations such as
{ a: :b } over {a: :b} and foo(b: 'bar') over foo( b: 'bar' ).
Merge pull request #10408 from patricksrobertson/convert_activemodel_to_new_hash_syntax

Convert ActiveModel to 1.9 hash syntax.