Updating to RxJava 2.1.5

Author: agonper

android-sensors/build.gradle

@@ -80,7 +80,7 @@ dependencies {
 
     // RxAndroid
     implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
-    implementation 'io.reactivex.rxjava2:rxjava:2.1.3'
+    implementation 'io.reactivex.rxjava2:rxjava:2.1.5'
 
     /*
     * Testing