Merge pull request #545 from irskep/fix_json_error

mrjob.conf aliases JSONDecodeError to ValueError if not using simplejson. Fixes #544.
added a test for HadoopJobRunner.path_exists() (it fails, as expected)
fixed HadoopJobRunner.path_exists()
Merge pull request #553 from davidmarin/path_doesnt_not_exist

Fix HadoopJobRunner.path_exists() (Issue #549)
just use ValueError, rather than the simplejson-specific JSONDecodeError
Merge pull request #555 from davidmarin/just_use_value_error

Just use value error
Fix for "unexpected ls line from hadoop" exception.

When using s3n:// urls the `hadoop.ls()` method threw an exception
as the output was not in the expected format.
Syntax errors (doh!)
Merged release 0.3.5 into master
Merge pull request #571 from sudarshang/merge_release_0_3_5

Merge release 0 3 5
Fixed local mode failing tests
Merge remote-tracking branch 'yelp/master'

Conflicts:
	mrjob/hadoop.py
Fix for using sn3:/// url's and the ls() function
LS rather than -test
added jobconf to MRJobStep
in theory, add steps-specific jobconf in hadoop and emr mode`
hadoop and emr mode now respect step-specific jobconf
moved and fixed test of _hadoop_conf_args()
Removed hardcoded s3n check.
Import