Import path of testsuite has been updated

### Changes
* [X] New import path in ``SourceInfo.testSuites``
* [X] ``revel.TestSuites`` is replaced by ``testing.TestSuites`` in a template of ``app/tmp/main.go`` file.

### Details
[#737](https://github.com/revel/revel/issues/737) and [#789](https://github.com/revel/revel/pull/789)