add 'ExtractHeader' method to object storage return types
update block storage 'Delete' acceptance tests to use 'Extract'
merge in 'DownloadResult' update
update comments to reflect change
refactor 'ExtractHeader' to 'gophercloud' proper
ExtractErrResult -> ErrResult; Extract -> ExtractErr
Merge branch 'master' of https://github.com/rackspace/gophercloud into ExtractHeader-method
embed 'gophercloud.Result' in 'ErrResult' and 'HeaderResult'
add `Err` to `CopyResult`
multi-line error check -> th.AssertNoErr
use th.AssertNoErr
use th.AssertNoErr
Merge pull request #277 from jrperritt/ExtractHeader-method

Extract header method