Streamline and clarify the introductory tutorial.

* Make the style match the Ruby tutorial more closely. Focus on a
  quick, concise demo.

* Factor out the requirements setup to only be provided in a separate
  page since most users will already have the requirements/won't have
  any trouble setting them up.

* Reorder the sections: focus on getting to the test code and
  explaining it. Running it is an important step, but requires very
  little explanation and delays getting to the meat of the tutorial.

* Make sure paths are consistent, especially since some text was
  shared between both Linux/Mac/Windows versions and used
  sauce-tutorial as the top-level and project directories on different
  platforms. Now we always use the layout
  sauce-tutorial/sauce-project.

* Note possibly different output since # of tests varies depending on
  which version of the sample code you use.
Improvements to 'first test' step.

Refactor the test class code to use included files since they are
replicated in the introduction tutorial and the first test tutorial
step. Tighten and rework the explanation of the first test code,
trying to omit details which should already be well understood, and
avoiding duplication between JUnit/TestNG samples. Fix segue into next
section.
Rework app testing intro.

Make sure we explain more up front instead of dumping large blocks of
code with little or no context. Explain overall structure before
delving into details. Explain what Selenium provides in general and
how we're using it in this particular instance.
Clean up intro to Java Helper library.

Explain that this is just explanatory and you are not supposed to
follow these instructions on the sample project. Also explain the
how you can see the effect of using the library on the Sauce Labs site.
Minor cleanup in Sauce Connect tutorial.
Explain test names for the Java helper library.
Add explanation to parallelism tutorial.

This tutorial was completely lacking any explanation. Explain the
general strategy for parallelization, then the specific example for
testing multiple browsers+platforms at the same time. Add note to
explain that they should try adding more platforms/browsers and
explain how they'll be able to tell that they are actually running in
parallel.