url: be stricter about detecting schemes
While the URL parser is very forgiving about what characters are
allowed in each component, it's useful to be strict about the scheme
so we don't accidentally interpret local paths with colons as URLs.
This restricts schemes to containing alphanumeric characters, dashes,
pluses, and dots (as specified in RFC 2396).
To run the tests, do:
cd tests/
python run-tests.py
See http://mercurial.selenic.com/wiki/WritingTests for
more information on writing tests.