Add linters to Travis

[matrixik]

How to add Shellcheck: https://github.com/koalaman/shellcheck/wiki/TravisCI

[matrixik]

Well, it's working but we have a loooooot warnings/errors...

[matrixik]

For Flake8 this are also nice:
https://pypi.python.org/pypi/flake8-comprehensions
https://pypi.python.org/pypi/flake8-copyright

[matrixik]

Found other two alternatives to Hound that support Shellcheck:
https://support.codacy.com/hc/en-us/articles/213632009-Engines
https://docs.codeclimate.com/docs/list-of-engines

There is also open source https://github.com/coala/coala/ that have many integrations:
https://coala.io/#/languages
Need to be run in travis, how to use coala in Travis with Docker:
http://coala.readthedocs.io/en/latest/Users/Docker_Image.html

[matrixik]

Splited into #263 and #264