React to Http.Core rename.

Author: Tratcher

src/Microsoft.AspNet.Hosting.Interfaces/project.json

@@ -2,7 +2,7 @@
     "version": "1.0.0-*",
     "description": "ASP.NET 5 Hosting interfaces.",
     "dependencies": {
-        "Microsoft.AspNet.Http.Core": "1.0.0-*",
+        "Microsoft.AspNet.Http.Abstractions": "1.0.0-*",
         "Microsoft.AspNet.FileProviders.Interfaces": "1.0.0-*",
         "Microsoft.Framework.NotNullAttribute.Internal": { "type": "build", "version": "1.0.0-*" }
     },