Streamline introductory tutorial, clean up extended tutorial, fill in parallelism tutorial

This updates many of the tutorial steps. The first commit focuses on the introductory tutorial, clearing out everything but cursory discussion of dependencies, leaving those to the detailed tutorial. It also reorders the steps to get to the code faster.

A few commits tighten up and clarify explanations in the detailed, multi-step version of the introductory tutorial.

One commit cleans up the java helper library tutorial. The point of this tutorial was unclear before, a new intro explains what's going on in the tutorial and that the code is already in one of the tutorial files.

A few minor commits clean up issues in the Sauce Connect and Java helper library tutorials.

Finally, adds an explanation to the parallelism tutorial. It was basically just a code dump before, now there's an explanation of the general approach to parallelizing tests and how the specific example in the code works.