build: switch to Linux-native connect tunnel

This PR changes the way we establish a tunnel from Travis-CI to SauceLabs from the java version to a native Linux version. The main motivation here is to be able to better track down android disconnection issues as we can better control logging with the native version. But apart from this the change has other benefits:
* it produces nicer input for Karma tests
* makes the build faster (funny fact: native connect is ~3MB as compared to ~30MB for the Java version...) 

Other than this it should be functionally equivalent.