Fix test failure if client.cfg defines a logging_conf_file.

When /etc/luigi/client.cfg had a logging_conf_file entry, like

    logging_conf_file = /etc/luigi/logging.ini

test_cmdline_logger would fail with something like

    AssertionError: [call(None)] != [call('/etc/luigi/logging.ini')]
Provide dynamic loading of modules

This adds a new interface to Luigi that takes a module parameter on the command line

Eg. you can run
python something.py --module my_luigi_job FooTask --x 1 --y 2

Inspired by discussion in #365
Worker returns boolean value for add and run commands, depending on their outcome
Merge pull request #378 from spotify/erikbern/dynamic-module-loading

Provide dynamic loading of modules
Add a script to find all deps on the paths b/w task T and task S.
This is a practical way of finding all upstream tasks of task S
Merge pull request #365 from rantav/find-upstream-deps

Create a script to find upstream dependencies
More unit tests, interface.run returns success value
Merge pull request #379 from rtshadow/worker_returns_action_status

Worker returns action status
Merge pull request #371 from miku/test_cmdline_logger

Fix test failure if client.cfg defines a logging_conf_file.
Fixed issue with grouping keys when running locally

When running a job on the hadoop cluster unicode strings and str strings
are grouped to different reducers since we wrap repr() around the key.
This patch simulates that behaviour when running locally.
Merge pull request #383 from oldpa/master

Fixed issue with grouping keys when running locally