fix signature bug to use RAW_PATH_INFO

This fixes signature creation to use RAW_PATH_INFO.

Swift3 could not create correct signature in case of
using escaped character(e.g. %2F, %2D) in PATH_INFO,
because env['PATH_INFO'] was decoded(unescaped) by
eventlet.wsgi before a request arrived at swift3.
It caused signature mismatch and authentication failure.

This change enables swift3 to create signature from
RAW_PATH_INFO and fixes that bug.

Note: This patch works well only in later version than
      eventlet 0.9.17, because older version does not
      have RAW_PATH_INFO variable.
      When using older version, swift3 works in the same
      way as ever(use req.path of swob).

Signed-off-by: Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>
Merge pull request #37 from bloodeagle40234/raw-path-signature

fix signature bug to use RAW_PATH_INFO
Content-Range uses space after bytes

Our test expected "Content-Range: bytes=0-N", but this is incorrect.
The RFC-2616 14.16 clearly says:
  bytes-unit SP byte-range-resp-spec "/" ( instance-length | "*" )

This is different from Ranges where bytes=0-N is specified.
The wonders of Web standards!

If a version of swob sent the equal sign previously, it was wrong,
but now corrected.
Take care of 403 Forbidden HTTP error

Return AccessDenied error to client
instead of default InvalidURI when subsequents
request in pipeline return 403 error.