Make --lock default to True. Add --nolock to provide lockless functionality when needed
Make nolock default when using luigi.build
Fixed an issue introduced in 6330e9d0332e6152996292a39c42f752b9288c96

- Previous commit introduced a bug that would cause tasks not to be exposed if they changed name after creation
- Added a new unit test for this case
- Ended up removing a lot of the code introduced in the previous commit and replaced it with a much simpler mechanism
- Removed some unit tests for unregister() since I decided that method wasn't a good idea to have
Renames flag to --no-lock and adds warning when --lock is used
Makes getpcmd and thereby process locking MacOSX-compatible
include worker id and host in log output

Makes log output more usable for troubleshooting when somewhere a worker process is hung. The "is currently run by worker-RANDOM_NUMBER" error message will now include the host, and logs on that host will let associate it with the pid.
Adding my local Vagrant bits to gitignore
Adding a target and external task for EMR output stored on S3
Fixed bugs in hive.py
Merge pull request #316 from spotify/freider/lock_by_default

Use process locking by default when running on command line
Merge pull request #324 from bstempi/feature/S3EmrTarget

Feature/s3 emr target
Merge pull request #326 from actsasgeek/fix-hive-module

Fixed bugs in hive.py
use label for upstream dependency checkbox
Merge pull request #317 from erikbern/task-register-fixes

Fixed an issue introduced in 6330e9d0332e6152996292a39c42f752b9288c96
Merge pull request #323 from spotify/ulzha/worker_ref

include worker id and host in log output
Hotfixed an error caused by c75085b3c812c8054ef76d39676ab473e45b9600
squash merge flatten-strings branch
Update example_top_artists.rst

Fix spelling of "exercise".
Merge pull request #336 from mikepii/flatten-strings-2

Flatten strings (squash merged)
Merge pull request #337 from pswaminathan/patch-1

Update example_top_artists.rst