pip install iisignature does not work unless numpy is pre-installed

[jc-healy]

We suggest removing import numpy from the setup.py script.

[soerenwolfers]

One is the first lines of the readme says you have to have nummy preinstalled, although i agree that this would be better handled with an entry in setup_requires (not install_requires!)

Edit: it's already there

[bnikolic]

I think this is fixed by : https://github.com/bottler/iisignature/pull/21 which is merged