Add PhantomJS and SlimerJS support
Fix JScript runtime on Windows 8
Fix PyV8 error handling

PyV8 maps some Javascript errors to built-in Python exceptions since
r304.
https://code.google.com/p/pyv8/issues/detail?id=178
https://code.google.com/p/pyv8/source/detail?r=304
Fix inaccurate JS source pieces substitution
Optimize and simplify `encode_unicode_codepoints`
Fix typo
Merge pull request #15 from true-pasky/master

Some enhancements