Luigi

Fixes issue 41 - Thx to millawell and xaedes for the (simultaneous) PRs 40 and 42 .

Beta release. Many minor fixes, including a MANIFEST.in file, and updates in README.

Beta release. Updates in this release includes adjustments to be able to initiate workflow tasks from within workflow tasks.

See also [this release on PyPI](https://pypi.python.org/pypi/sciluigi/0.9.3b4).

Some notable changes in this release:
- Python 3 support
- Support for Amazon S3 data targets

Big thanks to jeffcjohnson for these contributions!

Maintenance release, with mainly some PyLint warnings corrected.

There is more to do, like adding more tests and fixing more pylint issues, but the library works and is used in production already.

This is mainly a bug-fix release, fixing some bugs and minor polish.

**Changes:**
- Added util methods to save/retrieve flat dicts to recordfiles 199f6f1
- Raise exception on nothing returned from workflow() method of Workflo… … ff9e27d
- Update README with Prerequisites and Install sections 54bfee1
- Remove unneccessary log init 6293c9c
- Don't log about logfile path more than once c2cafeb
- Proper spacing around code blocks in README aa8310a
- Bugfix: Must use same treatment of list of command parts in all ex\* f… … 1e028c3
- Handle problem with multiple jobs checking the same folder at the sam… … ab41eb7
- Update text about work in progress, in README