This commit adds support for most common accessibility
methods/attributes to the OakTextView component. In user's language,
VoiceOver users (i.e. blind and visually impaired users) can now use
TextMate to read and write text.
A few less used accessibility attributes remain to be supported -
especially AttributedStringForRange and StyleRangeForIndex which should
allow blind users to e.g. see and seek for spelling errors in text.
Zoom is an OS X accessibility feature that lets sighted visually
impaired users magnify screen content. This commit notifies Zoom of
changes of TextMate's cursor position on screen so that Zoom can
automatically follow the cursor when the user moves it.