added Travis-CI support.
added build status image for Travis-CI.
JBEHAVE-453: com.google.code.guice:guice:2.0.1 is not available from regular maven repos.

Solved by excluding xunit dependency on guice and added dependency on guice:2.0 that is available on Maven Central.
added quiet option to avoid build termination by Travis-CI.
removed install customization, increased mvn memory and suppressing Maven msgs about downloads.
ignoring default dependency installation from Travis-CI.
JBEHAVE-878:  Added CI pages to include Travis CI.
JBEHAVE-878 fixed build status image to point to official repo.