Fix org.eclipselabs.xtext.utils dependency resolution issue

- Add org.eclipselabs.xtext.utils dependency to target definition
- Make test dependencies non-optional (Tycho is configured
  to ignore optional dependencies in target-platform-configuration)
- Remove p2 dependencies from pom.xml
- Add .travis.yml config file to test the build with Travis CI
Merge pull request #7 from fsteeg/Test

Fix org.eclipselabs.xtext.utils dependency resolution issue