CI: install conda-verify per conda-build suggestion

Author: pavoljuhas

.travis.yml

@@ -60,7 +60,7 @@ before_install:
   - $NOMC || popd
   - $NOMC || source ~/mc/bin/activate base
   - $NOMC || conda update --yes conda
-  - $NOMC || conda install --yes conda-build jinja2
+  - $NOMC || conda install --yes conda-build conda-verify jinja2
   - $NOMC || conda create --name=testenv --yes python=${MYPYTHON_VERSION} coverage
   - $NOMC || conda config --add channels diffpy