Smack version correctly updated to 4.1.3. smackVersion constant added to build.gradle.

#502

app/build.gradle

@@ -50,6 +50,10 @@ repositories {
     mavenCentral()
 }
 
+ext {
+    smackVersion = '4.1.3'
+}
+
 dependencies {
     compile 'com.android.support:design:22.2.1'
     compile 'com.android.support:appcompat-v7:22.2.1'
@@ -62,9 +66,9 @@ dependencies {
     compile 'com.google.zxing:android-integration:3.1.0'
     compile 'com.jcraft:jzlib:1.0.7'
 
-    compile "org.igniterealtime.smack:smack-android-extensions:4.1.2"
-    compile "org.igniterealtime.smack:smack-experimental:4.1.2"
-    compile "org.igniterealtime.smack:smack-tcp:4.1.3"
+    compile "org.igniterealtime.smack:smack-android-extensions:$smackVersion"
+    compile "org.igniterealtime.smack:smack-experimental:$smackVersion"
+    compile "org.igniterealtime.smack:smack-tcp:$smackVersion"
     compile project('otr4j')
     compile project('MemorizingTrustManager')
 }