Update maven and bintray plugins

Author: friederbluemle

build.gradle

@@ -24,8 +24,8 @@ buildscript {
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:3.2.1'
-        classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.4'
-        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.4.1'
+        classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.8.4'
+        classpath 'com.github.dcendents:android-maven-gradle-plugin:2.1'
     }
 }