Tests

Added tests for models. 
You can put this inside ```before(:each)``` block. Also, I don't think that you should be using ```FactoryGirl.attributes_for(:answer)``` for ```@edited_answer``` because it is just the same with ```@answer```.

What you can do instead is to manually set the body of the answer in the params. So for example:
```put :update, :question_id => question, :id => @answer, :answer => { :body => 'asdf' }```

Then the following: ```expect(assigns[:answer].body).to eq 'asdf'```