Docker-hub

This release corrects json format(when using ``--format json`` flag) so that output can be piped into other commands for further processing.

Special thanks to jessestuart for contributing the fix: https://github.com/amalfra/docker-hub/pull/9

This release adds support for authenticating using DOCKER_HUB_USERNAME, DOCKER_HUB_PASSWORD envs.

nothing much, just readme update

This release adds login command with which you can authenticate to docker-hub. If unauthenticated will be querying docker hub without token and will list public resources only.

Fix docker login bug when docker client not installed

This release fixes a bug which prevents docker-hub from working in python 3. It also fixes user command bug where it was always displaying no results found.

Support for shorthand commands has also been added in this release. Following is the list of supported parameters:
* -h, --help show this help message and exit
* -u USERNAME, --username USERNAME The Docker Hub username
* -o ORGNAME, --orgname ORGNAME Your orgname
* -r REPONAME, --reponame REPONAME The name of repository
* -p [PAGE], --page [PAGE] The page of result to fetch
* -f {table,json}, --format {table,json} You can dispaly results in table, json formats