added paginate() command

- paginate() takes the same args as text() but returns a list of Text
objects (as many as necessary to fully display the string) rather than
drawing to the screen.
- each Text in the list can then be passed to plot() and will draw to
the same x/y location (unless overridden)
- Text objects returned by paginate() have additional `pg`, `pp`, and
`folio` attrs as convenience counters
- Text.overleaf spawns a new Text object whose content begins where the
previous one’s was clipped off
text(src='foo.xml') will now process inline styles

- previously the file’s contents would be displayed verbatim
- now, tags will be stripped before display and element names in the
xml file will be mapped to styles defined in the global stylesheet()
text(str=...) now accepts numeric args

- text(str=“42”) and text(str=42) are now equivalent