fixed class constructor shorthands

renamed parameters, added missing ones
updated library wrapper

see https://gist.github.com/derhuerst/0354bdc8faa081bb1895
added class contractor shorthands `i` and `r`

`sketch.i(a, b)` is a shorthand for `new sketch.Interval(a, b)`.
`sketch.r(a)` is a shorthand for `new sketch.Rendering(a)`