Update docker_remote_api_v1.14.md

It is a tar stream, you should mention that somehow.

Here is the proof:

```
	host:~$ docker run -t -i ubuntu:14.04 bash
	root@c39be4c7b7c8:/# echo "my file contents" > abc
	root@c39be4c7b7c8:/# cat abc
	my file contents
	root@c39be4c7b7c8:/# exit
	host:~$ curl -H "Content-Type: application/json" -d '{"Resource":"/abc"}' http://localhost:4500/containers/c39be4c7b7c8/copy
	abc0100644000000000000000000000002112402102531007674 0ustar0000000000000000my file contents
	host:~$ curl -H "Content-Type: application/json" -d '{"Resource":"/abc"}' http://localhost:4500/containers/c39be4c7b7c8/copy > response_content
	  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
	                                 Dload  Upload   Total   Spent    Left  Speed
	100  2067  100  2048  100    19  56968    528 --:--:-- --:--:-- --:--:-- 58514
	host:~$ tar xvf response_content
	abc
	host:~$ cat abc
	my file contents
```

Docker-DCO-1.1-Signed-off-by: Mustafa Akın <mustafa91@gmail.com> (github: SvenDowideit)
Update export, copy and build API to sat 'TAR STREAM' for all versions.

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Merge pull request #7929 from SvenDowideit/doc-tar-stream

Sven Dowideit 	Update export, copy and build API to say 'TAR STREAM' for all versions.