Incorporate tarr

Fix #20

Please note, that for me running the tests results in an error - seems unrelated to TARR, yet it is not a clean run:

```
$ python -m unittest discover
............................................................................./home/.../mETL/env/local/lib/python2.7/site-packages/SQLAlchemy-0.9.7-py2.7-linux-x86_64.egg/sqlalchemy/engine/default.py:573: SAWarning: Unicode type received non-unicodebind param value.
  param.append(processors[key](compiled_params[key]))
/home/.../mETL/env/local/lib/python2.7/site-packages/SQLAlchemy-0.9.7-py2.7-linux-x86_64.egg/sqlalchemy/sql/type_api.py:322: SAWarning: Dialect sqlite+pysqlite does *not* support Decimal objects natively, and SQLAlchemy must convert from floating point - rounding errors and other issues may occur. Please consider storing Decimal numbers as strings or integers on this platform for lossless storage.
  d[coltype] = rp = d['impl'].result_processor(dialect, coltype)
.....F..............................................................................................................................................................
======================================================================
FAIL: test_json_target (tests.test_target.Test_Target)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests/test_target.py", line 70, in test_json_target
    self.assertEqual( self.getHashForFile('tests/config/test_json_target.yml', delete = False), 'fd5ae206495b4e9dc624e0999eaf5082' )
AssertionError: '403792a11551a52a395d20268229f1b9' != 'fd5ae206495b4e9dc624e0999eaf5082'

----------------------------------------------------------------------
Ran 241 tests in 35.598s

FAILED (failures=1)
```