Feature/add accounts

Finally got some tests to pass on the accounts model. The 'belongs_to' test didn't pass for ages and I couldn't figure out why, it kept saying that it needed a foreign key. In the end I read the info on guides.rubyonrails and made the accounts migration have 'user_id', together with the 'belongs_to :user' property in the model. You had 'owner_id' in your email for that model, which didn't seem to work for me.

Gonna try implement some of the other models, and use more of the shoulda matchers. 

- Stas