Adding extra targets to Makefile so that IPython notebooks will be co…

…nverted to static HTML

for inclusion in the HOWTO directory. Requires installation of IPython to carry out conversion.

nltk/test/Makefile

@@ -4,14 +4,19 @@ TESTS = $(wildcard *.doctest)
 
 ERRS := $(TESTS:.doctest=.errs)
 
-HTML = $(TESTS:.doctest=.html)
+HTML = $(TESTS:.doctest=.html) $(IPYNB:.ipynb=.html)
+
+IPYNB = $(wildcard *.ipynb)
 
 .doctest.errs:
 	python ./runtests.py $< > $@
 
 .doctest.html:
 	rst2html.py $< > $@
 
+%.html: %.ipynb
+	ipython nbconvert $<
+
 all: $(ERRS)
 
 html: $(HTML)