Add missing type information to the API docs.

Sample changes 

http://emberjs.com/api/data/classes/DS.RESTSerializer.html#toc_tweaking-the-default-json
#### Before 
![screen shot 2014-10-13 at 11 07 08 am](https://cloud.githubusercontent.com/assets/54056/4615540/2cf7c90c-52eb-11e4-838e-d98a98b9d6fb.png)

#### After 
![screen shot 2014-10-13 at 11 07 00 am](https://cloud.githubusercontent.com/assets/54056/4615547/33a5aa44-52eb-11e4-9459-de21b6101703.png)


http://emberjs.com/api/data/classes/DS.Transform.html#method_deserialize
#### Before
![screen shot 2014-10-13 at 11 12 22 am](https://cloud.githubusercontent.com/assets/54056/4615571/5f59713e-52eb-11e4-932f-e4571edfea6e.png)

#### After
![screen shot 2014-10-13 at 11 09 13 am](https://cloud.githubusercontent.com/assets/54056/4615555/475beca6-52eb-11e4-9563-9c21346c56e1.png)