Ensure that web views are included in accessibility paths.

`UIWebView` is a class that forces its instances' presence in the accessibility hierarchy
even though they are not themselves accessible elements. Without including it in the
hierarchy, web views cannot be manipulated by Subliminal.
Ensure that the web view child element matching test case's view loads before the test case starts.

Just for safety. We intended to do this before--the app hook was already implemented,
it just wasn't used.
Merge pull request #87 from inkling/jeff/fix_slwebview

Fix matching web views.