[NEED REVIEW] Add option to use arbitrary elements with styling instead of img

I decided to take over the unused `emojify_tag_type` for this feature.

When set it instead uses the set element type with a classname of 'emoji-' + emojiType

I also added the CSS files with the grunt task to create them, and set up minification. 

I didn't add any examples or change any demo files, I will wait for your review before I move ahead on that. This is also lacking tests as well, I will address both issues after the design is finalized.

Thanks @hassankhan
```
When set, emojify uses this `emojify_tag_type` element with the class `emoji emoji-#{emojiname}` instead of an `img` with a `src` attribute.  Example valid values: `div`, `span`
```
maybe a small copy tweak to emphasize ability to use any element, and the format expected