Update requirements to elasticsearch >= 1.0

This inverts the monkeypatch so that we can continue to work with
ElasticUtils 0.90, but use elasticsearch-py >= 1.0. That makes things a
lot easier going forward.

Fixes #261
Fix infinite recursion when unpickling a mapping type instance
Merge pull request #262 from willkg/update-es-py

Update requirements to elasticsearch >= 1.0
Fix migration document to clarify versions

* update migration document to clarify ES versions
* clean up some langauge to make it clearer
Merge pull request #263 from batlock666/master

Fix infinite recursion when unpickling a mapping type instance
Add test case for infinite recursion issue when pickling
Add Bert Vanderbauwhede to CONTRIBUTORS
Change StandardError to Exception
Update CHANGELOG for 0.10.1
Fix issues with tests and django 1.7

Fixes #259
Update versions for 0.10.1 release
Merge remote-tracking branch 'upstream/master' into raw_search
Fixed slicing support.
Merge branch 'raw_search'