Editor code adds unnecessary permission on Android

Fixes googleanalytics#15

Call for ‘SystemInfo.deviceUniqueIdentifier’ causes Unity to add
READ_PHONE_STATE permission when building for Android, though this code
is never run and not included in the build. Wrapped in preprocessor
directives to prevent unwanted permission.

Author: emmanuellemm

googleanalyticsv3.unitypackage

@@ -27,6 +27,9 @@ limitations under the License.
   other than Android and iOS.
 */
 public class GoogleAnalyticsMPV3 {
+#if UNITY_ANDROID && !UNITY_EDITOR
+#elif UNITY_IPHONE && !UNITY_EDITOR
+#else
   private string trackingCode;
   private string bundleIdentifier;
   private string appName;
@@ -416,4 +419,5 @@ public void SetOptOut(bool optOut) {
     this.optOut = optOut;
   }
 
+#endif
 }