Don't CGI encode header query values in the signature string

When constructing the signature string parameter, values that are valid to include in the string should not be CGI encoded (even though they should of course be encoded in the final request). See http://stackoverflow.com/a/12616647/1056941

Encoding breaks the ability to specify an attachment filename via

    ?response-content-disposition=attachment; filename=foo.txt

because the semicolon and space get encoded, which leads to a SignatureDoesNotMatch error. 

(Encoding was introduced in the changes made for 1.11; the above worked in 1.10.)
Fixes #1822 Joyent list_machines is slower than it needs to be

[joyent|compute] list_machines unnecessarily fetches tags for each server
[cloudsigma] Add CloudSigma compute provider
[cloudsigma] Fix create request not expecting status 201
[cloudsigma] Make api location as an option (:cloudsigma_host)
[cloudsigma] Fix excon HTTPStatusError#response not having []= and failing on assignment of json decoded body
Merge pull request #1821 from ronen/patch-2

AWS S3 Invalid signature when using response-content-disposition=attachment with filename
Merge pull request #1593 from cloudsigma/master

Added provider for CloudSigma
fix broken test related to redacted excon error bodies
[cloudstack] fix broken mock test
Include all snapshots in FOG::AWS::RDS::Snapshots#all
Add Snaphost#each method with lazy pagination
[rackspace|storage] created a last_modified= method in the File class which works around a timezone bug in the swift service
Merge branch 'master' of github.com:fog/fog into utc_fix
Merge pull request #1808 from harryw/rds_snapshot_pagination

Include all snapshots in Fog::AWS::RDS::Snapshots#all
Merge pull request #1823 from rackspace/utc_fix

[Rackspace|Storage] last_modified= work around
[openstack|compute] Add mock method to list_address_pools
Merge pull request #1826 from frodenas/add_mock_address_pools

[openstack|compute] Add mock method to list_address_pools