add a prebuilt wheel for ecos for python >= 3.7

[cmj123]

Please add a prebuilt wheel for ecos for python >= 3.7

[cmj123]

More description - ECOS is a dependency used in pyportfoliopt 1.5.1 library for portfolio optimisation. I am working in Bloomberg BQuant platform with is based on python 3.7.1. It will be significantly helpful to have a prebuilt wheel for ecos for python >= 3.7