Update build tools, Kotlin, and Gradle (#534)

Update build tools, Kotlin, and Gradle

.travis.yml

@@ -1,7 +1,7 @@
 language: android
 android:
   components:
-  - build-tools-27.0.3
+  - build-tools-28.0.3
   - android-27
   - extra-android-m2repository
   - extra-google-m2repository

build.gradle

@@ -1,11 +1,11 @@
 buildscript {
-    ext.kotlin_version = '1.2.30'
+    ext.kotlin_version = '1.2.71'
     repositories {
         jcenter()
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.1.3'
+        classpath 'com.android.tools.build:gradle:3.2.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }

common.gradle

@@ -1,6 +1,6 @@
 android {
     compileSdkVersion 27
-    buildToolsVersion "27.0.3"
+    buildToolsVersion '28.0.3'
 
     buildTypes {
         release {

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Wed Jun 06 12:44:35 CEST 2018
+#Tue Oct 02 18:53:47 EDT 2018
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-all.zip