update documentation to use MRStep rather than self.mr()
updated examples to use MRStep instead of self.mr()
use MRStep instead of self.mr() in test jobs
oops, MRStep requires keyword arguments
stop using self.mr() in tests
use kwargs for JarStep and MRStep in test_job.py
added tests for deprecated jar() and mr() methods
Merge branch 'master' of github.com:Yelp/mrjob into mrstep_is_my_name

Conflicts:
	tests/mr_tower_of_powers.py
Merge pull request #832 from davidmarin/mrstep_is_my_name

MRStep is the new self.mr() (fixes #815)