Connections now use two separate threads for writing and listening

- this should avoid dead locks, specifically when connecting to Jabit :/
- also, Java 8 features are now allowed in modules not needed by Android clients

demo/build.gradle

@@ -14,6 +14,8 @@ uploadArchives {
     }
 }
 
+sourceCompatibility = 1.8
+
 task fatCapsule(type: FatCapsule) {
     applicationClass 'ch.dissem.bitmessage.demo.Main'
 }