Fixed stalling builds.

Builds were stalling due to ADT dialogs waiting on user interaction due to the
following errors:

1. Using stale version of Android SDK.
2. Installation of build-tools failing.
3. SDK path was not being properly set.

This fixes the following issue:

https://github.com/rgladwell/m2e-android/issues/196
Merged testing wiki page into contributors guide.
Upgraded to latest version of Tycho.
Added virtual machine to simulate Travis.

Added Vagrant virtual machine to simulate the Travis continuous integration
build. Added full documentation.
Check parent projects aren't configured as Android

Added test to verify that parent POM projects aren't configured as Android
projects.

This indicates this bug cannot be reproduced:

https://github.com/rgladwell/m2e-android/issues/151