NotViewer: the Traits Notification Viewer.

A basic TraitsUI viewer for traits notifications. It's easy to include it in an existing application to monitor and debug traits notifications. Simply drop these commands in an appropriate place:
```
from etsdevtools.traits_utils.not_viewer import NotViewer
ui = NotViewer().edit_traits()
```
This will open a UI from which you can start recording the events.

Here is a screenshot of the example script:
![screen shot 2014-10-03 at 20 56 45](https://cloud.githubusercontent.com/assets/314633/4511820/446b8984-4b39-11e4-9cdb-cc70fd1e556a.png)

how about a context manager? :P