remove extra mailto: from Mark Davis
bump target version
add text abount leading slashes on paths

Added text to section 2.2 reinforcing the fact that the first slash _is_ part of the path, and to 3.3 emphasising the requirement for a slash before the windows drive letter when there's an (empty) authority [closes #5]

Also moved RFC 5234 reference from informative to normative [closes #8]