Update building script.
Merge pull request #6 from zpbx/dev

Add `root` module.
Merge pull request #7 from zpbx/dev-test

Update unit test.
Merge pull request #8 from zpbx/dev-dom

Add `dom` module.
Merge pull request #9 from zpbx/build

Update building script.
Update `str` module and its unit tests.
Add some comments in test code.