get_auditlogpath/get_auditdirpath/get_wflogpath return absolute paths

[vnaum]

relative paths break logging if workflow changes working directory:
2017-12-19 14:50:43 | ERROR | Error in event callback for 'event.core.processing_time'
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/luigi/task.py", line 155, in trigger_event
callback(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/sciluigi/audit.py", line 76, in save_end_time
self.add_auditinfo('task_exectime_sec', '%.3f' % task_exectime_sec)
File "/usr/local/lib/python2.7/dist-packages/sciluigi/audit.py", line 26, in add_auditinfo
return self._add_auditinfo(self.instance_name, infotype, infoval)
File "/usr/local/lib/python2.7/dist-packages/sciluigi/audit.py", line 40, in _add_auditinfo
with open(auditfile, 'w') as afile:
IOError: [Errno 2] No such file or directory: 'audit/.audit_XXXXXXXXXworkflow_20171219_145030_384056/XXXXXXXXXXXXXXXXXXXXXXXXXXXX'

[samuell]

Hi @vnaum and many thanks for the pull request!

Let me have a look in the coming week or so, if I can manage to set up automated testing / CI, to have this automatically checked against the relevant python versions etc, and then come back.