Changes since v0.5
------------------

Added dependency tracking code from Tobias Abenius. This feature adds a 
'dependson' option to Sweave and allows a code chunk to depend on another
named chunk. If a code chunk is modified, then its subsequent dependencies
are re-run (rather than loaded from cache).


Changes since v0.4-4
--------------------

We now call the makeRweaveLatexCodeRunner directly rather than copying over
code from the Sweave function by hand. This hopefully will allow for
easier maintenance and fewer breakages.