Fixed doc typos in Repo
Merge pull request #60 from jwarwick/repo_typos

Fixed doc typos in Repo
Add belongs_to association
Support belongs_to association in preloader
Support belongs_to association join
Support belongs_to with assoc selector
Optimize and simplify preloader
Document associations
More association documentation.
Dont crash on nils in preloaded

We might get nil records when doing certain joins
Validator checks that the assoc selector join is inner or left
Split Entity into Model and Entity
Update ex_doc dependency
Document Entity/Model changes
Add datetime type
Add test for unsupported type
Join binding works if too few binds were specified

Closes #59.
Check that too many vars weren't bound in query

Closes #58.
Simplify entity primary key setting

Dont require setting primary key to nil when using custom primary key.
Refactor entity function generation