remove a script I used to reproduce a bug

* the bug has been fixed and released in raca 0.3.2
stop using the ETag header on manifest uploads for large files

* The rackspace docs say:

    A similar situation applies to the ETag header. If it is used in the
    PUT operation, it must contain the MD5 checksum of the JSON content.

* despite that, I'm finding that including the ETag header results in
  rackspace returning a 422 error.
* We're probably doing something wrong, but damned if I can pick it. In
  the short term, best to just remove the ETag header from manifest
  uploads (it's optional) to get large file uploads working again
The correct header is ETag, not Etag
Etag is not a real HTTP header, the correct capitalisation is ETag

* http://en.wikipedia.org/wiki/List_of_HTTP_header_fields
prepare for release
remove this unused constant