Lab: Web Technology

Covers
* HTTP (httplib, requests)
* XML (DOM, SAX or ElementTree)
* WSGI (wsgiref)
add Web Technology lab to Volume 3
add TCP/IP section

Outline rest of the lab.
explain JSON

Explain what JSON is and basic reading and dumping.
explain XML

Begin section on XML.  Explain the difference between DOM and SAX.
more xml content
Merged the first two MPI labs bc they are short
And took it out of tex doc
Changed the directories
Redid line breaks in hysteresis lab.
Simplified code in hysteresis lab.
Added some hints and updated some formatting.
Fixed some typos found by students.
initial commit of chat client/server

The grand culmination project of the lab.
Chat over HTTP using JSON.
First runthrough of key grammatical editing
Second round of grammatical edits
A few final touch ups
introduce concept of serialization.
Added a currently commented-out diagram using TikZ
Fixed typo and changed emdash to double hyphen