index uses force_index argument which isn't valid anymore

[willkg]

Travis is failing with this:

ERROR: test_unindex (elasticutils.tests.test_types.ModelTest)

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/mozilla/elasticutils/elasticutils/tests/test_types.py", line 122, in test_unindex

id_=obj1.id)

File "/home/travis/build/mozilla/elasticutils/elasticutils/__init__.py", line 1993, in index

force_insert=force_insert)

File "/home/travis/build/mozilla/elasticutils/local/lib/python2.7/site-packages/pyelasticsearch/client.py", line 96, in decorate

return func(*args, query_params=query_params, **kwargs)

TypeError: index() got an unexpected keyword argument 'force_insert'

I think that it's from pyelasticsearch 0.6 changes, but I haven't looked into it, yet.

[willkg]

Fixed by issue #162.