try skipping some npm cruft

Author: bollwyvl

.binder/postBuild

@@ -11,8 +11,8 @@ popd
 
 # install and validate python environment
 python setup.py sdist
-python -m pip install -v dist/pythreejs*.tar.gz
-python -m pip install -e .[test,examples,docs] --ignore-installed
+python -m pip install -v dist/pythreejs*.tar.gz --no-deps --skip-npm
+python -m pip install -e .[test,examples,docs] --skip-npm
 python -m pip check || echo "uh oh"
 
 # build docs