Trac #15531: upgrade pycrypto to version 2.6.1

Source Tarball: [[http://ftp.dlitz.net/pub/dlitz/crypto/pycrypto/pycrypt
o-2.6.1.tar.gz|pycrypto-2.6.1.tar.gz]]

URL: http://trac.sagemath.org/15531
Reported by: ohanar
Ticket author(s): R. Andrew Ohana
Reviewer(s): Volker Braun
Trac #15532: upgrade networkx to version 1.8.1

Source Tarball: [[https://pypi.python.org/packages/source/n/networkx/net
workx-1.8.1.tar.gz|networkx-1.8.1.tar.gz]]

URL: http://trac.sagemath.org/15532
Reported by: ohanar
Ticket author(s): R. Andrew Ohana
Reviewer(s): Volker Braun
Trac #15511: upgrade rpy2 to 2.3.8

Source Tarball: [[https://pypi.python.org/packages/source/r/rpy2/rpy2-2.
3.8.tar.gz|rpy2-2.3.8.tar.gz]]

URL: http://trac.sagemath.org/15511
Reported by: ohanar
Ticket author(s): R. Andrew Ohana
Reviewer(s): Volker Braun
Trac #15512: upgrade sympy to version 0.7.4

Source Tarball: [[https://github.com/sympy/sympy/releases/download/sympy
-0.7.4/sympy-0.7.4.tar.gz|sympy-0.7.4.tar.gz]]

URL: http://trac.sagemath.org/15512
Reported by: ohanar
Ticket author(s): R. Andrew Ohana
Reviewer(s): Volker Braun