v0.10.0: better layout, added \marginpar

general:

• implemented \marginpar
• finished \parbox alignment combinations, all should work now
• fixed a few more whitespace issues, esp. in restricted horizontal mode; still some more left to go...

layout:

• layout can now be changed using \setlength
• implement default layout values for 10pt, onecolumn, oneside options
• margins and \textwidth: calculate their percentages relative to \paperwidth
• layout is still responsive; to make it static, use an absolute --paperwidth in the CSS

picture environment:

• implemented \qbezier and \cbezier
• implemented \oval
• implemented \multiput
• \line, \vector, \[qc]bezier: add room for linewidth using bbox()
• fixed \vector arrow head: it now ends exactly at the line end and properly scales with the linewidth
• fixed \put outside of a picture environment
• fixed picture offset

other fixes:

• HTML: set the charset to UTF-8
• API: optional arguments always have "?" appended => "o" is now "o?"
• little parser fixes
• more tests, extended the playground