Update package.json with repo field

Howdy. 

Just noticed that this module does not have a repository field, which upon installtion shows one of these:

```
npm WARN package.json colony-compiler@0.6.12 No repository field.
```

If there is a specific reason why this is not included, then nevermind this. If not, please see attached PR :)

... and now back to playing with my brand new tessel!