Version 0.3.0: Multibye modifiers and high-bit ranges.

This release improves multibyte handling. Codepoints are kept together, such that a regex like λ+ now matches "λλλ", and ranges and bytes expressed with \x syntax can cover the whole u8 range, not just the ASCII lower portion of it. With some care this allows for construction of useful character sets, so long as they happen to be dense in the Unicode codepoint spectrum.