Replace `dependencies` section by `frameworkAssemblies` in `net45` target (#340)

Jint/project.json

@@ -20,8 +20,8 @@
   },
   "frameworks": {
     "net45": {
-      "dependencies": {
-        "System.Diagnostics.Contracts": "4.0.0"
+      "frameworkAssemblies": {
+        "System.Diagnostics.Contracts": "4.0.0.0"
       }
     },
     ".NETPortable,Version=v4.0,Profile=Profile328": {