Update dependencies (#906)

PyYAML 5.1.2 -> 5.2 https://github.com/yaml/pyyaml/blob/master/CHANGES
flake8 3.6.0 -> 3.7.9 https://github.com/PyCQA/flake8/tree/master/docs/source/release-notes
paho-mqtt 1.4.0 -> 1.5.0 https://github.com/eclipse/paho.mqtt.python/blob/master/ChangeLog.txt
platformio 4.0.3 -> 4.1.0 https://github.com/platformio/platformio-core/releases
protobuf 3.10.0 -> 3.11.1 https://github.com/protocolbuffers/protobuf/releases
pylint 2.3.0 -> 2.4.4 http://pylint.pycqa.org/en/latest/whatsnew/changelog.html#what-s-new-in-pylint-2-4-4

pylintrc

@@ -24,6 +24,7 @@ disable=
   useless-object-inheritance,
   stop-iteration-return,
   no-self-use,
+  import-outside-toplevel,
 
 
 additional-builtins=