Suggestion to upgrade http.py script to use Python3

[gregoryfoster]

The legis-graph project favors Python3 so I was surprised to find the http.py script requires Python2. I went through an exercise of upgrading the script to Python3, which turned out to be a little tricky since the script filename happens to override the http.server module namespace! I wanted to be sure to note that for future reference, and would be happy to update the project with the minimal changes necessary to make it Python3-compliant:

• Rename http.py to legis-graph-guides-server.py
• Update http.py to use http.server module
• Update legis-graph/render.sh reference to http.py

After making these changes, I'm successfully playing the guides in the Neo4j browser. Thank you!