Fixing bugs related to setting DateTime attributes.

Fixing:
 - https://github.com/illuminate/database/commit/be7246d44f4667e27a196cbf91225f758b862004#L0R906
 - https://github.com/illuminate/database/commit/be7246d44f4667e27a196cbf91225f758b862004#L0R916
 - https://github.com/illuminate/database/commit/be7246d44f4667e27a196cbf91225f758b862004#L0R919

Signed-off-by: Ben Corlett <bencorlett@me.com>
Merge branch 'patch-3' of github.com:bencorlett/database into patch-3

Signed-off-by: Ben Corlett <bencorlett@me.com>

Conflicts:
	src/Illuminate/Database/Eloquent/Model.php