Kinto-attachment

**Bug fixes**
- Fix invalid request when attaching a file on non UUID record id (122)

**Bug fixes**
- Fixes compatibility with Kinto 5.3 (fixes 120)

- Expose the gzipped settings value in the capability (117)

**Bug fixes**
- Make kinto-attachment compatible with both cornice 1.x and 2.x (115)

**Breaking change**
- Remove the `base_url` from the public settings because the
accurate value is in the capability.

**Protocol**
- Add the plugin version in the capability.

**New features**
- Prevent `attachment` attributes to be modified manually (fixes 83)

**Bug fixes**
- Fix crash when the file is not uploaded using `attachment` field name (fixes 57)
- Fix crash when the multipart content-type is invalid.
- Prevent crash when filename is not provided (fixes 81)
- Update the call to the Record resource to use named attributes. (97)
- Show detailed error when data is not posted with multipart content-type.
- Fix crash when submitted data is not valid JSON (fixes 104)

**Internal changes**
- Remove hard-coded CORS setup (fixes 59)