Upgrade to RxJava 2.1.13

Author: akarnokd

build.gradle

@@ -49,7 +49,7 @@ dependencies {
     signature 'org.codehaus.mojo.signature:java16:1.1@signature'
 
     compile "org.reactivestreams:reactive-streams:1.0.2"
-    compile "io.reactivex.rxjava2:rxjava:2.1.12"
+    compile "io.reactivex.rxjava2:rxjava:2.1.13"
 
     testCompile group: 'junit', name: 'junit', version: '4.12'