Update Readthedocs python interpreter to python 3.X

[AurelienJaquier]

Pyhton2.7 support for efel was dropped some time ago, but readthedocs is still using it and thus fails to build efel's docs. @wvangeit could you change this in the readthedocs settings please?

[wvangeit]

@AurelienJaquier , I think it's working now.
Two questions:

• Can you update the copyright year in the main page of the readthedocs doc
• Could you make a readthedocs config file in the efel repo. I have attached the current config.

[wvangeit]

Thx @AurelienJaquier