Update Appveyor CI to MSVC 2015
Update Appveyor CI to MSVC 2015

lovell/sharp,papandreou/sharp,brandonaaron/sharp,dtest/sharp,papandreou/sharp,digital-flowers/sharp-win32,brandonaaron/sharp,pporada-gl/sharp,digital-flowers/sharp-win32,leiyangyou/sharp,pporada-gl/sharp,papandreou/sharp,chrisriley/sharp,digital-flowers/sharp-win32,chrisriley/sharp,papandreou/sharp,mcanthony/sharp,pporada-gl/sharp,cmtt/sharp,dtest/sharp,lovell/sharp,brandonaaron/sharp,mdimitrov/sharp,dtest/sharp,dtest/sharp,leiyangyou/sharp,brandonaaron/sharp,brandonaaron/sharp,mcanthony/sharp,mhirsch/sharp,mdimitrov/sharp,mcanthony/sharp,pporada-gl/sharp,leiyangyou/sharp,chrisriley/sharp,digital-flowers/sharp-win32,mdimitrov/sharp,mhirsch/sharp,lovell/sharp,digital-flowers/sharp-win32,mdimitrov/sharp,cmtt/sharp,lovell/sharp,mcanthony/sharp,chrisriley/sharp,chrisriley/sharp,pporada-gl/sharp,lovell/sharp,lovell/sharp,mcanthony/sharp,digital-flowers/sharp-win32,mdimitrov/sharp,cmtt/sharp,dtest/sharp,digital-flowers/sharp-win32,cmtt/sharp,mhirsch/sharp,papandreou/sharp,leiyangyou/sharp,mhirsch/sharp,leiyangyou/sharp