Fix tests: version parsing failed against ES 1.4.0.Beta1
Fix aggregations when running ES 1.4.0.Beta1

And also add support for "doc_count_error_upper_bound" that was introduced
in ES 1.4.0.Beta1.

Closes #1025
Fix script filter test on ES 1.4.0.Beta1
Fix alias tests on ES 1.4.0.Beta1
Fix #1026: Get endpoint should allow 404
Merge branch 'develop' of https://github.com/elasticsearch/elasticsearch-net into develop