Support for custom preview component

[go1dfish]

Would be nice to be able to specify a custom component for previews in order to support customized markdown parsers.

[andrerpena]

This is a good idea.. I'll keep this open

[andrerpena]

I'll make this as part of an effort of decoupling the components and making react-mde more flexible:
Relevant thread: #51

[andrerpena]

I'm now implementing the ability for your to select each command you'd like (#58) , and right after that, I'll improve the composability of react-mde.

This is the next task in the queue.

[go1dfish]

Sweet. We're looking at using this for https://github.com/decred/politeiagui and currently we use the Snudownd markdown parser and are likely to customize from there.

[andrerpena]

Thank you very much for considering using react-mde in your project.

After further consideration, I think the only way to make react-mde to support multiple previews is by breaking it down into 3 separate components and NPM packages (the toolbar, the textarea and a full-blown including the preview). This is because, even though I can strip react-mde in separate components in a single NPM package, the peerDependence to showdown will still be there. And having multiple NPM packages will complicate my life now.

I think I'll have to stick with showdown for now =/