Patch version bump (v1.21.4)

* Enable retries with Container#wait

Patch version bump (v1.21.3)

* Enable use of docker cache

Version bump (v1.21.2)

* Timeout error doesn't have a response

Patch version bump (v1.21.1)

Make error messages pertain to the errors

Minor version bump

Add support for turning off ssl_verify_peer

Minor version bump (v1.20.0)

Features:

Add container rename

Bug fixes:

Docker::Error::ConfictError to Docker::Error::ConflictError
Docker::Image.build_from_dir is now threadsafe

Minor version bump v1.19.0

Updates Remote API to 1.16
Adds exit code to Docker::Exec#start!
Calls `close_write` on IO if necessary after STDIN attach ends

Minor version bump (v1.18.0)

Add support for calling a block for each line when pulling an image

Minor version bump v1.17.0

* Add support for saving Images
* Use the correct connection when refreshing an Image
* More robust implementation of pushing images

Patch version bump 1.16.1

This version has a more robust version of Docker::Image.create.