Update .travis.yml
Update .travis.yml

add python 3 builds
pythonnet/pythonnet,QuantConnect/pythonnet,dmitriyse/pythonnet,yagweb/pythonnet,pythonnet/pythonnet,AlexCatarino/pythonnet,dmitriyse/pythonnet,yagweb/pythonnet,AlexCatarino/pythonnet,AlexCatarino/pythonnet,vmuriart/pythonnet,yagweb/pythonnet,vmuriart/pythonnet,denfromufa/pythonnet,denfromufa/pythonnet,QuantConnect/pythonnet,Konstantin-Posudevskiy/pythonnet,yagweb/pythonnet,denfromufa/pythonnet,vmuriart/pythonnet,Konstantin-Posudevskiy/pythonnet,AlexCatarino/pythonnet,dmitriyse/pythonnet,QuantConnect/pythonnet,Konstantin-Posudevskiy/pythonnet,pythonnet/pythonnet