Test handling of missing <html> tag

Fixes #555.

The testcase in the issue isn't entirely correct. If the </title> tag is
omitted, the <p> tag is actually in the <title> and won't be picked up
by querySelectorAll.

Tried to replicate the original test case as closely as possible,
verified with Chrome.
Test handling of missing <body> tag

Fixes #389.
Test handling of more non-standard markup

Fixes #88.
Test .innerHTML with less-than character

Fixes #652.

Could not reproduce bug behaviour with htmlparser2. Was this already
fixed?