CoolProp installation instructions

[puncan]

Consider removing the recommendation to do a manual install of CoolProp. With my Ubuntu 16.04 setup, the "get it directly from the development server" link they provide worked when the manual install did not after many attempts.

[momargoh]

@puncan. OK, I have removed the recommendation but kept in the instructions. On my system it's been the opposite, CoolProp from pip does not install properly whereas from the Github source code it does