Install packages for blender bundled python
To get BlenderCAM to run, you need shapely and numpy. At least in macOS, blender comes with a bundled python version. The packages need to be installed in the bundled site_packages, but since the bundled python doesn't provide pip, you need to install it manually.
Installing pip, then shapely and numpy
cd /Applications/Blender.app/Contents/Resources/2.78/python wget https://bootstrap.pypa.io/get-pip.py ./bin/python3.5m ./get-pip.py --prefix /Applications/Blender.app/Contents/Resources/2.78/python ./bin/python3.5m bin/pip3 install shapely numpy