Merge pull request #139 from LCTT/dependabot/pip/matplotlib-3.1.0

Bump matplotlib from 3.0.3 to 3.1.0

Author: LuuMing

requirements.txt

@@ -14,7 +14,7 @@ execnet==1.5.0
 future==0.17.1
 idna==2.8
 kiwisolver==1.1.0
-matplotlib==3.0.3
+matplotlib==3.1.0
 more-itertools==7.0.0
 numpy==1.16.1
 pandas==0.24.2