Aligned public method behavior on _BaseUpdater impls.
* check_update() accepts filenames, file-like objects, _Element,
  and _ElementTree instances.

* clean() accepts filenames, file-like objects, _Element, and
  _ElementTree instances.

* update() accepts filenames, file-like objects, _Element and
  _ElementTree instances.

* clean() returns ramrod.UpdateResults.

* Removed _BaseUpdater.cleaned_fields _BaseUpdater.cleaned_ids
  attributes.

* clean() and update() now returns ramrod.UpdatResults instances.
  This means they not longer set self._cleaned_fields or
  self._cleaned_ids.

* Removed _BaseUpdater._init_cleaned()

* ramrod.update()

* Moved clean() method to _BaseUpdater.

* Added stub _get_disallowed(), _get_duplicates(), and
  _clean_disallowed() methods to _BaseUpdater. Impls must
  override these methods or a NotImplemented() error is
  raised.

* Added test_clean() test to _BaseDisallowed unittest.TestCase

* Updated docstrings to reflect new return values and parameter
  types.
Made clean() and update() methods return a copy of the input node
if it receives an instance of _Element or _ElementTree.

* ramrod.utils.get_etree_root() : Added `make_copy` parameter.
Added docstrings to stix v1.0 _get_duplicates. Override base _get_duplicates() to return an empty dictionary
Added missing implementations of _get_duplicates and _clean_duplicates
Added more documentation to override _get_duplicates() methods, providing better explaination for the override.
Merge pull request #3 from bworrell/update-results

Update results