Add shibboleth-common as a dependency, clarify documentation, change version reference in documentation

On my system, mvn package fails without shibboleth-common, so I added it to pom.xml as a dependency.

I also added the lib directory where you're supposed to put duo.jar and made the documentation a bit clearer about where to put things.

Finally, I changed the version number from 0.1 to 0.2 in the README.