Add a CONTRIBUTING.md file

[vickash]

There are a some simple fixes that we should make before 0.12. I'm creating a separate issue for each one. If you can solve any of these problems and want to contribute, read the explanation of the problem and submit a pull request in response to the relevant issue.

Add a CONTRIBUTING.md file

See #55 (comment) where I explain to @X-Mort-X how to use dino from source. This should be included in CONTRIBUTING.md.

Also it should request that you submit pull requests against *-wip branches instead of master. Inclusion of tests. Add examples when writing code for new components, etc.

I'm probably leaving stuff out, so anything else of relevance can be discussed in this issue.

Also, Bootstrap's CONTRIBUTING.md looks like a good structure to follow: https://github.com/twbs/bootstrap/blob/master/CONTRIBUTING.md