Update our rationale for setting the `DEVELOPER_DIR` environment variable.

We no longer need to specify this so that the Xcode 4.6 toolchain will be used
instead of Xcode 5--Xcode 5 is now the default--but it's probably still safest
to set this so that the default toolchain will be used instead of any developer
previews' (lingering Xcode 5 previews, or Xcode 6 DPs, looking ahead).
Protect against `UISearchBarTextField` returning an attributed string from `-accessibilityValue` in iOS 7.
Correctly match table view header child elements on iOS 6.1 and 7.

We did not previously recognize that instances of `UITableViewSectionElement`
mocked table view headers because those elements failed our
accessibility-identifier-syncing check in `-[UIView elementObject:isMockingViewObject:]`.
However, we still were able to match table view header child elements precisely
_because_ we did not realize that instances of `UITableViewSectionElement`
were mock views, and so would simply include them in the accessibility path
as accessibility elements returning `YES` from `-[NSObject willAppearInAccessibilityHierarchy]`.

In iOS 7, instances of `UITableViewSectionElement` _do_ synchronize accessibility
identifiers with the views they mock, but once we recognized those elements
as mock views we then failed to include them in the accessibility hierarchy,
as our test table view header isn't itself accessible and also isn't of a class that
forces the presence of mocking views in the accessibility hierarchy.

We now compare elements' and views' accessibility frames,
if their accessibility identifiers do not synchronize, to properly identify
mock table view headers on iOS 6.1; and we include those headers
in the accessibility hierarchy by allowing elements that mock accessibility
children of table views.
Include an object's accessibility hint in its accessibility description.
Update the expected values of web view child accessibility element attributes for iOS 7.
Update the visibility tests with respect to the behavior of `UIAElement.isVisible` in iOS 7.
Prevent test case views from laying out under the nav bar on iOS 7.
Ensure that the `SLTextViewTestViewController` XIB uses the Xcode 4.6 format.

So when I edit it, it won't become incompatible with Xcode 4.6.2
which Travis continues to use for the time being.
Move the `SLTextViewTest` text view down a bit.

If it's right underneath the nav bar and the tests are running on iOS 7,
UIAutomation will hit the nav bar back button when it tries to tap the text view
--either because iOS 7 nav bar back buttons have giant hit areas or
UIAutomation's sloppy, I dunno.
Update Subliminal for `UIAElement.hitpoint` returning
`-[NSObject (UIAccessibility) accessibilityActivationPoint]` on iOS 7.
Retrieve alerts' titles using `UIAElement.name`.

Rather than from their title labels' text, because those labels are at different
paths on iOS 6 and iOS 7--on iOS 7, the title label is within a scrollview--
--but on both iOS 6 and 7, the text of that label is the alert's name.
Update `SLAlert` for the new structure of `UIAlertView` in iOS 7.
Update the maximum amount of time that an alert might take to be dismissed.

It is a bit longer on iOS 7 than previously (and will not harm anything
to be longer across the board).
Programmatically scroll scroll views in the iOS 7 Simulator.

In the iOS 7 Simulator, scroll views' pan gesture recognizers fail to cause those views
to scroll in response to UIAutomation drag gestures: a scroll view (and its pan gesture
recognizer) receives the touches involved in the gesture, but something inscrutable
goes wrong in the view's response to that gesture.

Subliminal uses a private UIAccessibility API to programmatically scroll the views
(with a higher degree of fidelity than `-setContentOffset:` would afford, e.g. the
private API notifies the delegate of appropriate scroll events as if the view
was being dragged). This method's usage need not be obfuscated because
it is compiled for the Simulator alone.
Update the README to announce iOS 7 support. (fixes #32)
Merge pull request #93 from inkling/jeff/32_xcode5

Support iOS 7 (fixes #32).