Use options in config as grunt intended

[kengoldfarb]

Proposal that we use a more standard grunt config format of:

grunt.initConfig({
    swig: {
        options {
            generateSitemap: true
        },
        dev: {
            options{
                generateSitemap: false
            },
            src: [**/*.swig],
            dest: 'www/'
        },
        prod: {
            src: [**/*.swig],
            dest: 'www/'
        }
    }
});