add a subsection for installation from conda-forge (#1740)
add a subsection for installation from conda-forge (#1740)

Summary:
After existing for close to a year and considering the quality (IMO) of the collaboration since then,
I believe it would be reasonable to also mention the conda-forge packages in `INSTALL.md`.

WDYT mdouze beauby?

Pull Request resolved: https://github.com/facebookresearch/faiss/pull/1740

Reviewed By: mdouze

Differential Revision: D26870699

Pulled By: beauby

fbshipit-source-id: 17465cd5c9f138f041d394d61fccd086bcafc3c7

facebookresearch/faiss,facebookresearch/faiss,facebookresearch/faiss,facebookresearch/faiss