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.
Fixes for canonicalize_url, object ACL query, signed URLs
Issue #49 - fixed Date and ExpireDate checking logic
Cleaned up PEP8 and Flake8 formatting errors.
canonical_string refactoring + fix typing in middleware comment
Merge pull request #53 from vitoordaz/master

canonical_string refactoring + fix typing in middleware comment
Undo part of patch by Willys

A regression in tests was introduced by commit
12163092ab793c6d0a1b2883f5e1858b97991e22, intended to
fix issue #49.

Willys' code actually seems to make sense, but I chose
to undo it because
 - It appears to be extraneous to the issue #49
 - It does not fix the tests or remove the now-unused constant

Someone should re-fix it properly. But for now I prefer tests
continue to pass.
Merge pull request #54 from zaitcev/master

Undo part of patch by Willys