Closes #753

Closes #751

When dragging there is no src attribute needed on the dummy image.

Though it doesn't seem to have any observable effect on Chrome.

@peterkroon Where does the image actually show up?

It produces a bogus horizontal scrollbar there.

(codemirror2 -> codemirror)

Closes #736

Closes #737

Closes #738

Was "};" => "}\n;" before, "};" => "};\n" now.

Markdown mode: fixed issue with [bracket quoted words] that aren't actually links being tokenized as links

Now that the scroller div has its own vertical scrollbar, we no longer
need to explicitly update the scrollbar during updateDisplay.

https://groups.google.com/forum/?fromgroups#!topic/CodeMirror/PKCQHasHuhE%5B1-25%5D

This is a temporary kludge. I hope we'll be able to find a better
solution. (This should bring back the flicker issue on Lion.)

Issue #727

Makes its behavior match the documentation, and the behavior or .next().

Issue #724

String.prototype.charAt returns '' (empty string) for characters outside the range of the string.

Suggested implementation for issue #722

Issue #721

Produces less noisy change objects when pressing enter.