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
Replace 'resolves' with 'fulfills'
Revise statements about #qunit-fixture
Merge pull request #583 from kategengler/integration-testing-guide-edits

Integration testing guide edits
Add keyDown helper to testing guide
Merge pull request #584 from kategengler/add-new-keydown-helper-to-testing-guide

Add keyDown helper to testing guide