Add integration testing guide
Update integration.md

Remove passing `app` to `findWithAssert`. Thanks @teddyzeenny.
Remove passing app to wait helper in testing guide
Merge pull request #1 from teddyzeenny/testing-guide

Remove passing app to wait helper in testing guide
Remove references to advanceReadiness

Thanks @ebryn.
Merge pull request #580 from kategengler/testing-guide

Add integration testing guide