Update networkx and xlrd
...in an attempt to kill some deprecation warnings under Python 3.7.
@@ -18,7 +18,7 @@ latexcodec==1.0.5
MarkupSafe==1.0
matplotlib==3.0.0
more-itertools==4.3.0
-networkx==2.2
+networkx==2.3
numpy==1.15.2
oset==0.1.3
packaging==18.0
@@ -41,4 +41,4 @@ sphinxcontrib-bibtex==0.4.0
sphinxcontrib-websupport==1.1.0
toml==0.10.0
urllib3==1.23
-xlrd==1.1.0
+xlrd==1.2.0
