Asana Integration

Really like Watson and wanted to be able to use it with [Asana](http://www.asana.com), a popular web-based project management tool that we use. I integrated this in the same fashion as with the other remotes. Setup involves specification of an API key obtained from Asana, a workspace and a project within that workspace. Issues are then pushed to the specified project and tagged with:

* fix/todo/review etc
* 'watson'
* filepath

e.g:

```python
# blah.py

if __name__ == '__main__':
    # [todo] - a todo
    print 'Hello world'
```

![screen shot 2013-12-11 at 13 44 32](https://f.cloud.github.com/assets/1734057/1724224/142e4b92-626b-11e3-8b49-c0e8597e038c.png)

I think this would be useful to others also so may be worth pulling it in.

--Mike