Issue228 default separator to dict

[Didou09]

Fixes in devel issue #228

Default separator is now '.' instead of '_'
=> renders better the nested dict structure
=> allows to use '_' in attributes names

[pep8speaks]

Hello @Didou09! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2019-11-04 13:19:05 UTC

[Didou09]

Only python 2.7 not passing
=> merge because we are dropping python 2.7 (cf. PR #231 )

[lasofivec]

I reviewed the changes, even if I have no actual comment.
I think for code sanity is better if we always review each other's PR.

[Didou09]

Agreed, I'll try to stick to that from now on