QUnit Composite addon - Major cleanup

This is a reworked version of PR #408 that @Krinkle and I worked through. It puts the Composite addon into a much better state for further incremental improvement commits.

**Work done:**
 - Deleted 'index.html' as it was a pointless copy of the 'README.md'.
 - Renamed 'composite-demo-test.html' to 'composite.html' to match all of the other QUnit addons.
 - Added some special notes to the 'README.md'.
 - Reduced surface area of API to minimum.
 - Removed some useless code (`testStart` handler that repeated something that QUnit core already does)
 - _BUG FIX:_ Corrected issue in 'qunit-composite.js' with use of inline style vs. CSS class that prevent results from ever being expanded.
 - _BUG FIX:_ Moved lifecycle logging registration to inside of the `testSuites` call, otherwise this throws errors if the script is included on a test page that executes non-composite tests. Needs further hardening in a subsequent PR to prevent issues with calling `testSuites` multiple times and calling `testSuites` in conjunction with normal tests (both are edge cases).
 - Related to that bug fix: added an overloaded signature for `testSuites`, so you can now optionally pass in a string to be used as the module name internally.
 - etc.