Add homepage (index.html, mkd.js)

This commit lets you test this library in the browser.
based on the md2bbc (a failed test) index.html page
create test build scripts

tests/list_tests.py creates a JSON file (tests/testlist.json), that is read from tests/index.html.

This Python script (it should run on both Py2k and Py3k with no modifications) visits the whole tests/ folder looking for tests cases.

You can make it ignore some test files writing their path into tests/testignore.json
Refactor js test scripts

in this commit, the test evaluation is centralized in test/test_utils.js.
every test is run (in test/bbcode folder) by add_to_tests function.
it should have been committed in the previous commit. wtf