Faiss 1.7.0

Bump version to 1.7.0. (#1652)

Summary: Pull Request resolved: https://github.com/facebookresearch/faiss/pull/1652

Reviewed By: mdouze

Differential Revision: D26077948

Pulled By: beauby

fbshipit-source-id: 599ee61edd2425250948577cb55d145d9179ab25