Add spaces and digits to Parser::$regex_snippets.
First batch of space matching.

Todo;

* Some missing modifiers.
* Needs pattern that matches the opposite of space.
* Some instances where Textile allows wrong chars.

See #133
Lookbehind compilation errors.
Opposite of whitespace.
Some work on digits, footnote refs now support unicode.

Add test for unicode footnotes.
Update changelog.
Merge remote changes from branch 'master'.