Add final execution hooks to luigi, as well as batched counter increments

Change-Id: I6aba342a446a8b039ac6fcd7379cfce9f859f659
Reviewed-on: https://gerrit.spotify.net/gerrit/43537
TC-Compile-And-Test: Team City <teamcity@spotify.com>
Reviewed-by: Elias Freider <freider@spotify.com>

Conflicts:
	.gitignore
	luigi/hadoop.py
Merge pull request #20 from jcrobak/hive-script

separate functions for hive script/cmd.
Fix failure tracking for non-streaming jobs.

* move the @staticmethods to luigi.hadoop namespace.
* refactor all uses of those functions.
* clean up some random lint errors and imports.