Avoid unnecessary db query on index update

pks_seen is only needed if objects are removed from
index, so only compute it if necessary.
Improve pks_seen to not build an intermediary list.
Use HTML5 <input type=search> (closes #899)
Merge pull request #899 from acdha/html5-input-type=search

Search form <input type="search">
Use elasticsearch-py instead of pyelasticsearch.

elasticsearch-py is the official Python client for Elasticsearch.
Merge pull request #885 from HonzaKral/elasticsearch-py

Use elasticsearch-py instead of pyelasticsearch.
upgraded python3 in tox to 3.3

3.3 is a better target for haystack than 3.2, due to PEP414
Merge branch 'master' into avoid-pks-seen-on-update

Change smart_text into smart_bytes as in master

Conflicts:
	haystack/management/commands/update_index.py
Merge pull request #775 from stefanw/avoid-pks-seen-on-update

Avoid unnecessary, potentially huge db query on index update