Merge pull request #2369 from open-keychain/update_gradle_plugin_ssh_auth_api

Update android gradle plugin for sshauthentication-api

OpenKeychain/build.gradle

@@ -226,7 +226,7 @@ android {
             minifyEnabled false
             //proguardFiles = buildTypes.release.proguardFiles
             //testProguardFiles 'proguard-rules-test.pro'
-            
+
             multiDexEnabled true
 
             applicationIdSuffix ".debug"

sshauthentication-api/build.gradle

@@ -4,9 +4,10 @@ apply plugin: 'bintray-release' // must be applied after your artifact generatin
 buildscript {
     repositories {
         jcenter()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.2'
+        classpath 'com.android.tools.build:gradle:3.1.3'
         classpath 'com.novoda:bintray-release:0.8.0'
     }
 }