Found a couple of places that hard-code the version of the Maven GWT plugin and replaced them with the ${gwt.version} variable.  This addresses issue #58.
Merge pull request #91 from DavidWhitlock/issue-58-gwt-version-in-poms

Use ${gwt.version} for the version of the gwt-maven-plugin.  Found a couple of places that hard-code the version of the Maven GWT plugin and replaced them with the ${gwt.version} variable. This addresses issue #58.