Latest python-pcl not compatible with python 2.7

[fitter22]

Hi,
while debugging issue with our CI build I found a problem with python-pcl on Ubuntu 16.04. Looks like this commit: e7a7640, have modified the numpy requirements to numpy>=1.16.1,!=1.16.2. That requirement is being resolved by installing numpy in version 1.17, which is not compatible with python 2.7:
https://docs.scipy.org/doc/numpy-1.14.2/neps/dropping-python2.7-proposal.html
So building process ends with error message about having not supported python version.
https://github.com/numpy/numpy/blob/1acc8b73e4a3ebd4959b2a6079531987b47437c6/setup.py#L31

I've managed to build the python-pcl successfully on my machine by doing manual checkout to the commit pushed before the mentioned one, and using the numpy 1.14.

I would recommend to discard the latest numpy in python requirements (ofc if its not really necessary) to preserve better compatibility.