Update requirements.txt

requirements.txt

@@ -1,10 +1,10 @@
 certifi==2017.11.5
-flask==0.12.2
+flask==1.0.2
 flask-babel==0.11.2
-lxml==4.1.1
-idna==2.5
+lxml==4.2.1
+idna==2.6
 pygments==2.1.3
-pyopenssl==17.4.0
-python-dateutil==2.6.1
+pyopenssl==18.0.0
+python-dateutil==2.7.3
 pyyaml==3.12
 requests[socks]==2.18.4