better checking of invalid zipfiles + adapt to no throw behavior of libzip 0.11.1 - refs https://github.com/springmeyer/node-zipfile/issues/33
better checking of invalid zipfiles + adapt to no throw behavior of libzip 0.11.1 - refs https://github.com/springmeyer/node-zipfile/issues/33

CartoDB/millstone,mapbox/millstone,BHare1985/millstone