Attach command for Docker Client
Added AuthConfig to contain auth information (user, password, email) and support for X-Registry-Auth header on pull/push operations
Merge pull request #105 from harmanpa/authconfig

Added auth for pull/push operations to support private repositories
Added a test case for AttachCommand and fixed a typo in the javadoc
Attach command returns LogStream instead of InputStream
Changed docs for attachCommand
Merge pull request #104 from JWGmeligMeyling/attach-command

Attach command for Docker Client