travis: Fix in-place install for building widget catalog

egg_info command used to be invoked during .travis/install_orange.sh
(as a sub-command of setuptool's sdist; since biolabgh-3345 plain distutils
sdist is used)

.travis/build_doc.sh

@@ -22,7 +22,7 @@ done < <(echo "$images")
 echo -e 'all ok\n'
 
 # build Orange inplace (needed for docs to build)
-python setup.py build_ext --inplace
+python setup.py egg_info build_ext --inplace
 
 cd $TRAVIS_BUILD_DIR/doc/development
 make html