Update PostController to add a getPosts method.

Signed-off-by: Se7enChat <se7enchat@zoho.com>
Add post presenter.

Signed-off-by: Se7enChat <se7enchat@zoho.com>
Update PostInteractor and tests.
- Interactor methods on longer return values, but perform actions instead.
- Deleted integration tests for the time being.

Signed-off-by: Se7enChat <se7enchat@zoho.com>