BF: Fix 'testmanual' Makefile target

Assumption of working directory changed.

Author: mih

Makefile

@@ -94,8 +94,7 @@ unittest: build
 	@PYTHONPATH=.:$(PYTHONPATH) $(NOSETESTS) nibabel --with-doctest
 
 testmanual: build
-# go into data, because docs assume now data dir
-	@PYTHONPATH=.:$(PYTHONPATH) $(NOSETESTS) --with-doctest --doctest-extension=.rst doc/source/ doc/source/usecases
+	@cd doc/source && PYTHONPATH=../..:$(PYTHONPATH) $(NOSETESTS) --with-doctest --doctest-extension=.rst . dicom
 
 
 coverage: build