Add travis button

[guillep]

The readme should include the travis button like in these projects:

• https://github.com/sbragagnolo/taskit
• https://github.com/pillar-markup/pillar/tree/stable

It does not matter if the button is read, but we need quick feedback about it.

Broken window principle :)

[rbardenet]

I'll take care about it.

[rbardenet]

Hi @guillep . Don't I need additional rights to the repository to access the project's travis page ?

[guillep]

You should not need anything special. Can you access this link?

https://travis-ci.org/guillep/python-grocery-list

[rbardenet]

Yes, I can, thanks!