fix(docs): use io.Copy in the get logs example

[KatIsCoding]

Closes: #160

Problem

The "get logs" example in the README copied the log stream using stdcopy.StdCopy(os.Stdout, os.Stderr, logs), pulling in github.com/docker/docker/pkg/stdcopy. Readers following the example would either see garbled output or need an extra dependency that the SDK does not actually require for consuming ctr.Logs().

Root Cause

stdcopy.StdCopy decodes Docker's multiplexed stream format (an 8-byte header per frame carrying the stream type and payload length). The reader returned by ctr.Logs() is not in that multiplexed format, so feeding it to stdcopy.StdCopy results in an error, or no output if not handling the error.

Fix

• README.md: replace the github.com/docker/docker/pkg/stdcopy import with the standard library io package, and copy the logs with io.Copy(os.Stdout, logs).

Testing

• Documentation-only change; no tests affected. The updated example compiles and prints the container log output as expected.

[mdelapenya]

LGTM, thanks!