Added python linters and enabled travis CI to run linters

This commit adds python linters as it improves the code quality.
Travis CI is enabled to run linters on each PR to make sure it
follows the best practices and doesn't break the tool.

.travis.yml

@@ -0,0 +1,15 @@
+dist: xenial
+
+langauge: python
+
+python: "3.6"
+
+before_install:
+  - sudo apt-get update
+
+install:
+  - sudo apt install python3-pip
+  - sudo pip3 install -r test-requirements.txt
+  - sudo pip3 install tox
+
+script: tox .