Pymilvus

New Feature:
- Not support python 3.5 any more

* Incompatibly support hybrid functionality. The changed APIs are:
- create_collection()
- create_index()
- drop_index()
- insert()
- search()
* Delete type class MetricType, IndexType

New Feature:
- Upgrade method `load_collection()` to support specify partitions

Fixed issues:
- Fix wrong result on 'has_partition' with http handler 237