Use Ecto.DateTime record for datetimes
Convert datetime to records in driver instead

Needs to be done in the driver because that is the only place we have the
type information to do the correct conversion.
Add interval type and common datetime operations
Support custom primary key on associations

Closes #61.
Update to Elixir 0.10.2
Raise if no foreign_key set with no @ecto_model on associations
Remove dataset wrapper on Entity
Update README and examples
Minor README/example fixes
More docs for associations
Support boolean type on entity fields

Closes #71.
More docs
Add links to the README
Tidy up types
Don't keep the full parent record in assocations

For has_many we need the primary key of the parent for the Queryable
implementation.
Closes #69.
Improve error messages for association primary keys

Closes #66.
Fix build
Move primary key nil check for has_many to correct place
Fix HasMany/HasOne.new and add tests
Split up __ecto__ functions

Closes #65.