updated kotlin version

build.gradle

@@ -1,12 +1,13 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.2.30'
+    ext.kotlin_version = '1.2.31'
     repositories {
         jcenter()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.1'
+        classpath 'com.android.tools.build:gradle:3.1.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong
@@ -17,6 +18,7 @@ buildscript {
 allprojects {
     repositories {
         jcenter()
+        google()
     }
 }