Make pgcrypto rails 4 compatible by default

Not sure if anything else is needed or you want to check if attr_protected is installed and then generate attr_accessible if it is. 

Just thought I should get a discussion going. So please do tell if you feel like this could be done better. I have one question for you though I seem to be missing a key in my specs. I'd prefer if we could have that key available in the repo as well so that nothing is needed to make the tests run properly.

I'm unsure if my changes breaks any existing functionality though.