snippets for the biojs registry

Hey

this adds jHeatmap and its examples to the BioJS registry (as snippets).

Testing
-----------

You can test this locally by using 

```
npm install
npm run sniper
```
(inside of the jheatmap folder).

And open [http://localhost:9090/snippets](http://localhost:9090/snippets)

The BioJS registry runs browserify on all packages.
Then it displays the examples (aka snippets) with a server-side version of the biojs-sniper.
Settings for the snippets are set in the `package.json`.

Publishing
---------------

It is super-easy - just run `npm publish`. The registry will pick up your package and list + display it ;-)

Here is [an example](http://registry.biojs.net/client/#/detail/biojs-vis-msa) of how the output in the registry will look.

Remarks
--------------

I tried to make as few modifications as possible to your source, but if you continue to work on this library it would be excellent if you could split up your code into packages/modules. Tinier modules make it way easier to reuse your codebase. A good example is generally IO stuff
Plus there are existing libraries for data sorting, filtering and aggregation - no need to reinvent the wheel ;-)