new scientific notation format

Hi Everyone,

There is a new formatter in ticker.py called NewScalarFormatter. If you have
scientific notation in your plots, you may like the results. If you would
like to try it out, you need to change ScalarFormatter->OldScalarFormatter,
and NewScalarFormatter->ScalarFormatter. It will then be the default for
linear scale axes. I would appreciate feedback, it will hopefully become the
default at some point.

Darren