Updating and Adding Content

[peterstory]

I'm doing a careful read-through of the textbook, and making edits and more substantive changes as I go. The biggest changes I've made so far:

• Added a footnote with details about Python performance, since it is possible to build performant Python programs under certain conditions
• Added more details about Java vs C vs C++. Recent trends show the gap between Java and C++'s popularity diminishing, so I wanted to focus on more pedagogical reasons (e.g., complexity of language syntax).
• Removed use of the Java GUI, since it doesn't work in Runestone
• Fixed the Python code which reads test.dat