[#60] Add AppVeyor badge to README
[#60] Add AppVeyor badge to README

sirex/datapackage-py,okfn/datapackage-py,datapackages/datapackage-py,okfn/datapackage-model-py,datapackages/datapackage-py,okfn/datapackage-model-py,sirex/datapackage-py,okfn/datapackage-py