Lesson 2 (Rebased, touched)

Hi Folks,

I've cleanly rebased @agolding718's work onto where it should have forked from master so that it's independent of his Lesson 1 work.  I've also done a first pass through at editing.

@agolding718 - this is good work!  Sorry I couldn't give you feedback earlier, but I like the way this lesson is shaping.  I think we should try to get this merged in by mid-week, and defer major improvements (animating the robot motion, for example), to other pull requests.

I think we may need to introduce a slightly simpler function up front for them before we give them the robot control function.  Let's see how Lorena and the other students feel about it, but the ingredients we are introducing are:

* function definition
* parameters
* body
* control logic
* return statements

I think we should at least give them a function definition with parameters and return statements to understand before we introduce the logic of control statements.  One option would be to give an example of a robot that mindlessly just goes forward.  Another would be to define a function that does simple math (like converting Fahrenheit to Celsius).