Update script and slides after timed rereading.

Script:

- Set marks for slide change.
- Remove slide comments (already implemented), added a couple more.
- Don't read wireless testbed examples.
- Lots of small changes to ease readability.

Slides:

- Better phrase to build your own testbed.
- Fix location of towers slide.
- Include Community-Lab in title of testbed arch slide.
- Refocus frame of admins & researchers in testbed slide (show CN).
- Refocus frame of gatewayh includes server.
- Jump straight from researcher in testbed arch slide to slivers slide.
- Remove global slide for example.