Support for host config

* Warnings will now raise exceptions in unit tests
* Updated several tests to use host_config

* Deprecation warnings added in Client.start

Devices should be separated by colon separated string

Run Travis tests on Docker

Signed-off-by: Ben Firshman <ben@firshman.co.uk>

Totally bad test :( (written by me). The documentation and
code should match now. Many thanks to pranavs18 for spotting
the error and proposing the fix.

Fixed bug in utils.mkbuildcontext for BytesIO Dockerfiles

Fixed integration tests

Allow for pull as an option to docker build

Signed-off-by: Derek Hammer <derek.r.hammer@gmail.com>

Expand registry URL before login.

Enforce passing string as version param in ctor

Merge branch 'fix-env-variables-unicode' of github.com:maxcnunes/docker-py into maxcnunes-fix-env-variables-unicode

Fix expand_registry_url to be consistent with docker client.

In docker-py's auth.py the functions 'resolve_repository_name' and 'expand_registry_url' work together to result a hostname prefix to a base URL suitable for interaction as a Docker registry.

For example, "docker push foo.com/bar/baz" would try to resolve the hostname "foo.com".

These functions loosely correlate to 'ResolveRepositoryName' and 'newEndpoint' in the docker client code, respectively.

You can see from their implementations:
 - ResolveRepositoryName: https://github.com/docker/docker/blob/master/registry/registry.go#L191
 - newEndpoint: https://github.com/docker/docker/blob/master/registry/endpoint.go#L71

that neither of them appends 'v1' to the hostname during resolution.

This change simply removes the 'v1' suffix from these code paths, which enables docker-py to authenticate against private registries with which the docker client can already.

Allow ExtraHosts to be specified when creating a container