replaced simplejson with jyson, changed example to use a GremlinPipeline

Install jyson from the rexster-server directory with the following command::

  mvn install:install-file -DgroupId=com.xhaus.jyson -DartifactId=jyson -Dversion=1.0.2 -Dpackaging=jar -Dfile=jyson-1.0.2.jar
added jyson dependency in pom.xml should be installed manually see last commit for the command