Simplify requirements and bump networkx to latest 1.x version.

requirements.txt

-decorator==4.0.2
-funcsigs==0.4
-matplotlib==1.4.3
-mock==1.3.0
-networkx==1.10
-nose==1.3.7
-numpy==1.9.2
-pbr==1.6.0
-pyparsing==2.0.3
-python-dateutil==2.4.2
-pytz==2015.4
-readline==6.2.4.1
-six==1.9.0
-wheel==0.24.0
+matplotlib
+networkx==1.11
+gnureadline