Reorganize documentation and source.

Simple edit to reorganize documentation and source, and flesh out a bit
more literate text.
Add simple test harness struct.

Add a test harness struct to enable easier test suite creation.
Fix buffer allocation bug(s).

Apart from writing even more documentation and adding a few more test,
the main bug fixed with this commit concerns array bounds checking and
overflow issues with the wp_suites variable. In particular, the
wp_test_suite_new function has been improved and corrected, as well as
the math around bounds checking in various places throughout the code.