Allow plain objects in "globals" option

Right now globals option support just list of json files.

    'compile-handlebars': {
        all: {
            ...
            globals: ['file1.json', 'file2.json']
        }
    }

This pull request allows to provide plain JS objects for globals as well.

    'compile-handlebars': {
        all: {
            ...
            globals: [
                'file1.json', 
                'file2.json',
                {
                    property1: 'value1',
                    property2: 'value2'
                }
            ]
        }
    }