fixed bug in dependency validation

error messages should be a lot more helpful now
Add compression (scp -C) for RemoteTarget get/put
make luigid state file path configurable

Use `state-path` option of the [scheduler] section to adjust
the state path file location.

Addresses [#188](https://github.com/spotify/luigi/issues/188).
Added missing import to interface.py
Issue #199 - move reducer initializing to base class

Change-Id: I54bc142b4f17789a7bc4c06e50b4a87b12149091
Merge pull request #200 from edwardnewett/master

Issue #199 - move reducer initializing to base class
Merge pull request #186 from erikbern/validate-dep-error

fixed bug in depdency validation
Merge pull request #191 from sisidra/master

Add compression (scp -C) for RemoteTarget get/put
Merge pull request #195 from miku/issue-188

make luigid state file path configurable
Merge pull request #196 from davidxia/master

Added missing import to interface.py
Merge remote-tracking branch 'upstream/master'
- fix all cases of    logging.foo(format_string % args)
- fix logging calls from  logger.foo(format_string % args)   into
  logger.foo(format_string, *args)
- and make a small optimization to error line accrual in
  run_and_track_hadoop_job.py
Revert "- don't turn exceptions that occur that might ultimately cause a pipe"

This reverts commit 10769bc1ca8750ac5df33874dea3f087895dc9b3.

This is to make the diff and history a bit cleaner.
Merge branch 'logging' of https://github.com/JonNelson/luigi into logging