Page MixTeen, sprint 0
Corrections page Mixteen après Hangout du 27/3

Logo de Cyril
Intro de Aude
mexteen intro :
- made the main logo / main text centered
- made it look better on smartphones
Merge pull request #1 from mpetitdant/mixteen-intro-updates

mixteen intro :
Merge pull request #250 from gquintana/mixteen-2014-init

Initialisation Mixteen 2014