Fix unable to parse error(As reported by SJoseph)

Ignore EOFError raised by stderrout.read_nonblock, since with
sufficiently big stdout, small stderrout and small buffer_size, err
will reach EOF before the stdout is completely read. This would
cause the graders output to be truncated.
Remove unnecessary comments.
Reload graders' config after sleep on edx client

Every time edx_client wakes from sleep it reloads the autograders'
config.
Initial specs for feature.

Unit tests for private methods load_due_date load_grace_period.
Fix specs for load_due_date and load_grace_period
Add part specific due_date grace_period capability

Now load_due_date and load_grace_period have the below priority:
1)Part specific due date and grace period in autograders config file
2)Assignment specific due date and grace period in autograders config
3)Default values in EdXClient

If part_name is not supplied in load_due_date or load_grace_period,
they revert back to their previous version
added a space in .travis.yml
Merge branch 'unable_to_parse_fix' into test
Merge branch 'test'