Update psycopg2

[brien-givens]

Description:
The psycopg2 package is renaming their wheel package to psycopg2-binary: http://initd.org/psycopg/articles/2018/02/08/psycopg-274-released

For the lifespan of the Psycopg 2.7 cycle, the psycopg2 PyPI package will still contain wheel packages, but starting from Psycopg 2.8 it will become again a source-only package.

Importing postgres currently results in this warning:

UserWarning: The psycopg2 wheel package will be renamed from release 2.8; in order to keep installing from binary please use "pip install psycopg2-binary" instead. For details see: <http://initd.org/psycopg/docs/install.html#binary-install-from-pypi

Updating psycopg2 >= 2.5.0 to psycopg2-binary >= 2.7.5 fixes the issue - tested locally.

[chadwhitacre]

Thanks @brien-givens! :-)