deployr api: improved exception handling and script failure messaging

[alee]

We are incorrectly trying to convert HTTP 400 responses from DeployR as JSON, which lead to the following stack traces and useless information being passed back to the client. The information from DeployR is a bit confusing however, for some reason when we try to run a script with invalid parameters (i.e., sdb=31 on luxedemo Figure 1), it generates the following Project param not specified on projectDirectoryList call error:

[miracle.core.deployr|check_status:155] results response: 400: Project param not specified on projectDirectoryList call, request denied.
[2016-07-03 07:57:29,999: ERROR/MainProcess] Task miracle.core.tasks.run_analysis_task[0834c421-507f-4670-8688-d7e1c7bba5f7] raised unexpected: ValueError('Extra data: line 1 column 4 - line 2 column 1 (char 3 - 79)',)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/celery/app/trace.py", line 240, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/celery/app/trace.py", line 438, in __protected_call__
    return self.run(*args, **kwargs)
  File "/code/django/miracle/core/tasks.py", line 37, in run_analysis_task
    job_name='{}-{}'.format(analysis.name, output.pk))
  File "/code/django/miracle/core/deployr.py", line 238, in run_script
    job = Job(session)
  File "/code/django/miracle/core/deployr.py", line 156, in check_status
    try:
  File "/usr/lib/python2.7/site-packages/requests/models.py", line 812, in json
    return complexjson.loads(self.text, **kwargs)
  File "/usr/lib64/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib64/python2.7/json/decoder.py", line 368, in decode
    raise ValueError(errmsg("Extra data", s, end, len(s)))
ValueError: Extra data: line 1 column 4 - line 2 column 1 (char 3 - 79)