major refactoring in progress -- saving progress
implemented (hopefully) importing font heights. completely untested
finished the refactoring. changes include:
    renamed PageState into PageReceiver and made it into the
        superclass for PageTextReceiver (removed all of
        the function-forwarding nonsense)
    streamlined the text positioning logic and placed it all
        into PageReceiver
    fixed text rendering with kerning (tj)
    fixed a matrix multiplication bug when processing
        text displacement
    implemented (but did not test) vertical-mode text
    implemented (but did not text) importing font-heights
        for composite fonts
updated readme
removed bad variable reference