imbrium revision

• added tests for new utils module

• name changes of predictor classes:

univarstandard => univarpure
BasicMultStepUniVar => PureUni
univarhybrid => univarhybrid (unchanged)
HybridMultStepUniVar => HybridUni
multivarstandard => multivarpure
BasicMultSTepMultVar => PureMulti
multivarhybrid => multivarhybrid (unchanged)
HybridMultStepMultVar => HybridMulti

• tox added

• outsourced Binder demo notebook to https://github.com/maxmekiska/ImbriumTesting-Demo

• new README.md