update version number to 4.0.0 (#593)

Author: JoC0de

src/NuGetForUnity/Editor/Ui/NugetPreferences.cs

@@ -28,7 +28,7 @@ public class NugetPreferences : SettingsProvider
         /// <summary>
         ///     The current version of NuGet for Unity.
         /// </summary>
-        public const string NuGetForUnityVersion = "3.1.3";
+        public const string NuGetForUnityVersion = "4.0.0";
 
         /// <summary>
         ///     The current position of the scroll bar in the GUI.

src/NuGetForUnity/package.json

@@ -1,7 +1,7 @@
 {
     "name": "com.github-glitchenzo.nugetforunity",
     "displayName": "NuGetForUnity",
-    "version": "3.1.3",
+    "version": "4.0.0",
     "description": "A NuGet Package Manager for Unity",
     "unity": "2018.4",
     "keywords": [