Pycondor

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**Changes**:

* Fixes bug where Jobs that have no arguments, when submitted from a Dagman, were not included in the dag submit file. (See :issue:`33`)

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**Changes**:

* Adds subdag support. Now Dagman objects can be added to other Dagman object with the new ``add_subdag`` class method.

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**Changes**:

* Adds ``retry`` option to the Job ``add_arg`` method. This allows the user to specify the number of times to re-submit this node in the Job if the node fails.
* Adds ``name`` option to the Job ``add_arg`` method. If a name is specified, then a separate set of log, output, and error files will be generated specifically for that node.
* Adds ``tests`` directory in ``pycondor``!

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**Changes**:

* Adds ``use_unique_id`` option when creating a Job object. This will then create a separate error, log, and output file for each of the arguments in the Job ``args`` list.
* Adds ``extra_lines`` option when creating a Dagman object (similar to the Job object).
* Replaces all occurances of ``os.system()`` with ``subprocess.Popen()``. This won't affect anything the user touches, just modernizing under-the-hood stuff.

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**Changes**:

* Adds ``request_cpus`` attribute to Job object to make it easier to request a specified number of CPUs.
* Adds ``pycondor.get_queue()`` feature to get ``condor_q`` information.
* Job and Dagman object methods now return ``self``.
* Fixed typo in logger formatting.