upgrade sympy to version 0.7.4

[ohanar]

Source Tarball: sympy-0.7.4.tar.gz

Component: packages: standard

Author: R. Andrew Ohana

Branch/Commit: u/ohanar/sympy0.7.4 @ fb8c07f

Reviewer: Volker Braun

Issue created by migration from https://trac.sagemath.org/ticket/15512

[sagetrac-git]

Changed commit from b5128bc to 409fdb6

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

[409fdb6](https://github.com/sagemath/sagetrac-mirror/commit/409fdb6)

Merge branch 'master' into sympy0.7.4

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

[fb8c07f](https://github.com/sagemath/sagetrac-mirror/commit/fb8c07f)

sympy: don't restrict to python2 for cleanup

[sagetrac-git]

Changed commit from 409fdb6 to fb8c07f

[vbraun]

Reviewer: Volker Braun

[vbraun]

comment:4

lgtm