Use static analysis/code quality service

[fdiblen]

Using a service like Codacy or Sonarcloud will give more insights about improvements you can make.

[egpbos]

Duplicate of #95

[egpbos]

Actually, #95 was just about PyLint, but Codacy does a bit more. Most issues there are just from PyLint. However, it also does code duplication detection, which is kinda nice. Maybe we could use that later on to clean up the code a bit more.

It was very easy to activate, so I did, the results can be browsed here: https://app.codacy.com/gh/spokenlanguage/platalea/dashboard

It should be easy to add a badge to the README at some point, so I'll just leave this open to remind us.