rearranging furniture
added `src` kwarg (and html/rtf support) to text()

- reads from a file path or url to provide the string
- if the name ends in an `html` or `rtf` extension, the styling will be
preserved (after a fashion) rather than applying the current font()
settings to it
- links to stylesheets in fetched html files won’t be followed (but
style blocks defined within the page *will* be used)