Back out the upgrade of the MEL dependency

Author: nblumhardt

src/Serilog.Extensions.Logging/project.json

@@ -9,7 +9,7 @@
     "iconUrl": "http://serilog.net/images/serilog-extension-nuget.png"
   },
   "dependencies": {
-    "Microsoft.Extensions.Logging.Abstractions": "1.1.0",
+    "Microsoft.Extensions.Logging.Abstractions": "1.0.0",
     "Serilog": "2.3.0"
   },
   "buildOptions": {