Add a generic `bower` command

This allows for calling bower in the components root directory, e.g.:

    manage.py bower list
    manage.py bower list -- -j
Merge pull request #12 from blueyed/bower-command

Add a generic `bower` command
Merge branch 'master' into develop
Fix test
Add support of bower install and bower freeze commands
Fix actual work
Update readme
Update documentation
Bump version to 5.0