Let users choose between psycopg2 binary or source

[browniebroke]

Subject: Let users choose between psycopg2 binary or source

Feature or Bugfix

• Bugfix

Purpose

On our system we want to install the source version of psycopg2, but because of #60, we are also getting the binary version when we install django-redshift-backend.

Adding extra_requires to let the use choose which version they want.

Quoting the psycopg2 documentation:

If you are the maintainer of a published package depending on psycopg2 you shouldn’t use psycopg2-binary as a module dependency. For production use you are advised to use the source distribution.

Relates

• Let users choose between psycopg2 and psycopg2-binary #60

[shimizukawa]

LGTM!