Add notes to bill

Currently no way to visualize the note later, this will come in a later PR https://github.com/my-koop/service.website/issues/295

![image](https://cloud.githubusercontent.com/assets/4157103/5194660/c108b9d4-74de-11e4-93d3-0efc6f6c17f7.png)

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@huboard:{"order":0.15625,"milestone_order":27,"custom_state":""}
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a note