Formatting fixes in the README
Add tests for <unicode-range> tokens.
Fix tokenization of <unicode-range> tokens, per spec change.
Import <unicode-range> tests.

Merge commit 'f38c4c09383407be08977001b1e9870e1bac8197' into unicode-range
Merge pull request #14 from SimonSapin/unicode-range

Fix tokenization of <unicode-range> tokens, per spec change.
Use char::from_u32 to cast to char