* Initial commit
* Added extra_headers
* Added freeze() method to ClientRequest which produces a 'read-only' copy of a request suitable for retrying the send operation
* Additional methods for FrozenClientRequest
* Fix
* Increased crates versions
* Fixed a unit test. Added one more unit test.
* Added RequestHeaderWrapper
* Small fixes
* Renamed RequestHeadWrapper->RequestHeadType
* Updated CHANGES.md files
* Small fix
* Small changes
* Removed *_extra methods from Connection trait
* Added FrozenSendBuilder
* Added FrozenSendBuilder
* Minor fix
* Replaced impl Future with concrete Future implementation
* Small renaming
* Renamed Send->SendBody
