workshops/test/__init__.py: Use an explicitly relative import
workshops/test/__init__.py: Use an explicitly relative import

With the absolute_import future for Python 2 compatibility [1].  This
avoids errors like the following on Python 3:

  $ make test
  ...
  ======================================================================
  ERROR: workshops.test.test_event (unittest.loader.ModuleImportFailure)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/usr/lib64/python3.4/unittest/case.py", line 58, in testPartExecutor
      yield
    File "/usr/lib64/python3.4/unittest/case.py", line 577, in run
      testMethod()
    File "/usr/lib64/python3.4/unittest/loader.py", line 32, in testFailure
      raise exception
  ImportError: Failed to import test module: workshops.test.test_event
  Traceback (most recent call last):
    File "/usr/lib64/python3.4/unittest/loader.py", line 312, in _find_tests
      module = self._get_module_from_name(name)
    File "/usr/lib64/python3.4/unittest/loader.py", line 290, in _get_module_from_name
      __import__(name)
    File "/.../amy/workshops/test/__init__.py", line 1, in <module>
      from test_event import *
  ImportError: No module named 'test_event'
  ...

[1]: https://docs.python.org/2/library/__future__.html

pbanaszkiewicz/amy,shapiromatron/amy,pbanaszkiewicz/amy,swcarpentry/amy,wking/swc-amy,pbanaszkiewicz/amy,wking/swc-amy,vahtras/amy,vahtras/amy,swcarpentry/amy,wking/swc-amy,shapiromatron/amy,swcarpentry/amy,wking/swc-amy,shapiromatron/amy,vahtras/amy