Fixed bug in utils.mkbuildcontext for BytesIO Dockerfiles
- resetting dockerfile seek position to 0 after dockerfile.getvalue() is called
- prevents traceback on line utils.py line 43
- 'IOError("end of file reached")' in tarfile.py
Should be done for StringIO objects as well
Expand registry URL before login.
Change remove_image to check if image is a dictionary and use Id value if it is.
Remove trailing whitespace.
Add support for filtering images and containers

[`filters` is a json encoded value of the filters (a map[string][string]) to process on the images list. ][1]
The tricky thing is that we must convert boolean value to string and any filter value to list to make a `map[string][string]` json format

[1]: https://docs.docker.com/reference/api/docker_remote_api_v1.14/#list-images
Merge branch 'filters' of github.com:irachex/docker-py into irachex-filters

Conflicts:
	docker/utils/__init__.py
	docker/utils/utils.py
	tests/utils_test.py
Updated tox.ini to also run utils_test.py tests
Merge branch 'irachex-filters'
Merge pull request #333 from alexliew/change_remove_image

Change remove_image to check if image is a dictionary.
Bumped version
Updated ChangeLog
Changed assertIn to assertTrue(... in ...) (2.6 support)
Merge branch 'master' of github.com:dotcloud/docker-py
Merge branch 'master' into 0.6.0-release
exec -> execute
Fixed integration test
Fixed ChangeLog section titles
Merge pull request #386 from docker/0.6.0-release

Release 0.6.0
Back to dev version