Add a wordCharacters option to the JavaScript mode
[comment addon] Fix two border cases

Issue #2768
[dialog addon] Add more options

* closeOnEnter: whether or not the dialog should be closed when you
  press enter with it focused. Defaults to true.

* closeOnBlur: whether or not the dialog should be closed when the
  textfield or button loses focus. Defaults to true.

* onClose: a callback that will be called when the close function
  completes.

* onInput: very similar to onKeyDown, but uses the input event instead
  of keydown. Just an additional event handler basically.
[dialog addon] Small style tweaks

Issue #2777
[search addon] Add classes to styled elements in dialogs

Closes #2776
Make indentSelection not scroll cursor into view

Closes #2769
Work around Webkit returning a null rectangle for a zero-size wrapped space

Issue #2775
Mark release 4.5.0
Bump version number post-4.5.0