Use **type** instead of **account_type**

GhUser is defining account_type as attribute, but
account_type cannot be unserialized directly
as the JSON field retrieved from github is type.

We could either define a post processor or use
back ticks to use type as valid attribute (type
is a reserved word)

Also, a method to retrieve an user profile without
access token has been added
Merge pull request #3 from juandebravo/feature/get-anonymous-user

Use **type** instead of **account_type** while retrieving an user profile