Adding a "variable" option for JSONP

We can now either require a callback to be returned or we can choose to have the JSON value set in a variable. Example: var myvariable = {"foo": "bar"};
Moving the GPG signing plugin to a specific deployment profile
Providing a way to intialize the variableParameter and callbackParameter names via constructor or setter.

This feature is a simplification for those who use Java Configuration (without web.xml).
Upgrading the servlet API to 3.0.1
Updating the readme to provide a doc for the java config
Merge branch 'master' of github.com:vdurmont/jsonp-filter into vdurmont-master
Merge branch 'vdurmont-master'
Merge pull request #4 from earldouglas/merge-pr-1

Merge pr 1