Add EventEmitter support and an option for looping...

Hey,

This change adds support for EventEmitter by @Wolfy87 (https://github.com/Wolfy87/EventEmitter).  Eg:

    var swipe = new Swipe(document.getElementById('slider'));
    swipe.events.on( 'next', function() {
        console.log( 'attempting to move to next slide' );
    });

    swipe.events.on( 'prev', function() {
        console.log( 'attempting to move to previous slide' );
    });

    swipe.events.on( 'slide', function( index, slide ) {
        console.log( 'moving to slide index: ' + index );
    });

    swipe.events.on( 'transitioned', function( index, slide ) {
        console.log( 'transitioned to slide index: ' + index );
    });

    swipe.events.on( 'begin', function() {
        console.log( 'beginning auto sliding' );
    });

    swipe.events.on( 'stop', function() {
        console.log( 'stopping auto sliding' );
    });

    swipe.events.on( 'resume', function() {
        console.log( 'resuming auto sliding' );
    });

It also adds an option to control if the slider should loop.  Eg:

    var swipe = new Swipe(document.getElementById('slider'), {
        looping: false // will not loop on next/prev calls at last/first slide
    });

Let me know what you think.  I'm open to making changes if this doesn't quite meet your expectations.