Updated to GTK3.

Switched to logilab-astng for generating the code tree, since the compiler package was deprecated in python 2.6.
When the outline can't be generated due to invalid code in the source text, an error is displayed instead of the outline. Selecting the error will jump to the location in the source where the error was raised by astng.
Improved the handling of the outline pane; it will now completely hide when non-python source is in the text area, and reappear when needed.
Display of from-imports (ie, from foo import bar) and aliased imports (ie, import foo as bar) are different.
More attributes display, and look slightly different. For example, attributes on a class are no longer prefaced with "self.".
Attributes now have an icon.
Removed the "outline rendered in N seconds" label.
Changed the stock icon used for the outline pane.