Initialize global network.

This is recommended, since it avoids the overhead of implicitly doing
the setup for each session.
Support PIL or Pillow.

Clean up examples so that Pillow can be used rather than the deprecated
PIL library.
FIX: Interpret linesize as absolute value.
Merge pull request #40 from billyshambrook/master

Initialize global network and example PIL/Pillow support.
Document the motivation for the fix
Merge branch 'linesize'; fixes one use of negative linesizes
Docs: Improve index a little
Docs: Be able to write Sphinx in library headers
Docs: Basic overview of time in the libraries