0.0.11

You can now have any name for attachments in Model. This also allows having multiple uploads per model. E.g. the following now works.
```
processable :avatar, Attachment
processable :image, Attachment
```
You will need avatar_meta_data and image_meta_data fields, now.

Many thanks to @mrbongiolo for implementing this.

0.0.10

Require Dragonfly 1.0.12 or above and change internal API accordingly. Thanks @acaron for fixing that!

0.0.9

Add Task#delete! which allows to delete files in task blocks.

0.0.8

Introduce Model::Writer and Model::Reader in case you don't like Model#image's fuzzy API.

0.0.7

Task#process! (and the delegated File#process!) now delete the original version of an attachment if process! is used to replace the latter.