ENH added an orange cite us button on the front page
FIX cite us buttong made blue bar span too much
DOC added testimonials

from INRIA and evernote
FIX forgot evernote's logo
ENH added telecom to the testimonials
DOC updated evernote's testimonials
ENH added AWeber's testimonial
ENH added carousel back on front page for testimonials
ENH better spacing on the first page
ENH testimonials img are now centered.

More spacing around button
FIX typo in testimonials

Thanks @jaquesgrobler
Polishing on "Who's using scikit-learn"
DOC: layout tweaks