Implemented option to include images attached to tweets.

So far working with my own feed - let me know if I haven't followed your approach anywhere or if there are any improvements you'd like me to make and I'll update.

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`config.showImages` defaults to `false`, but if set to `true`, the tweet's image will be extracted (if present) and included within a `div.media` element after the `p.tweet` element - this currently extracts the largest image provided (if multiple sizes are attached).
exampleUsage.js has been updated to demo functionality, and `twitterFetcher_min.js` has been re-minifed to include latest changes.