Upgrade gradle to 3.1

build.gradle

@@ -21,10 +21,11 @@ buildscript {
     repositories {
         maven { url 'https://maven.google.com' }
         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"
         classpath "io.realm:realm-gradle-plugin:4.3.1"
     }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Sat Sep 02 02:16:27 PDT 2017
+#Tue Mar 27 18:57:37 EDT 2018
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip