Very minor updates to Python tutorial
Very minor updates to Python tutorial

While working on bug19280 I had the Python tutorial
open in an edit buffer and make some small edits
to improve readability as I went along.

No release notes.  No changes to the code. The html
file looks OK in the browser.

Change-Id: Iddf9fb163b6dcb2d13e20c2359d345629dd3f22d

franzinc/agraph-python,franzinc/agraph-python,franzinc/agraph-python,franzinc/agraph-python