Corrected Class package

SessionHandler and HashSessionManager both reside in org.eclipse.jetty.server.session package as can be seen here: 
http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/server/session/HashSessionManager.html
http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/server/session/SessionHandler.html
Merge pull request #58 from vrozkovec/master

Corrected Class package