add etag header
Merge pull request #180 from wenderen/etag-header

add etag header
rustup for clone trait
Merge pull request #186 from hyperium/declone

rustup for clone trait
add allow header
Merge pull request #188 from wenderen/allow-header

Allow header

Closes #174
feat(cargo): prepare for crates.io release.
(release) 0.0.11.