Mobile Swipe and more!

This release includes better mobile swipe experience.

Props added includes
infinite boolean
onPause function
onPlay function

I've renamed the scss file so if you were previously using
@import "../node_modules/react-image-gallery/src/ImageGallery";
please update to
@import "../node_modules/react-image-gallery/src/image-gallery";

merged in pull request #43 and #45, and other minor bug fixes.