Update to gradle 4.4 and plugin 3.1.0.

build.gradle

@@ -11,7 +11,7 @@ buildscript {
     }
 
     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"
     }
 }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Thu Mar 22 10:22:36 CET 2018
+#Thu Apr 05 14:47:17 PDT 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