Update Otimiazação de Imagens

Almost final content after first revision
Move Otimização de Imagens from draft
Merge branch 'content/otimizacao-de-imagens'

Conflicts:
	app/_drafts/2014-8-16-otimizacao-de-imagens.md
Update Otimização de Imagens hero
Improve title readability over image

A better text-shadow, covering more image and adding the right contrast
to the text and image, were implemented. This improve readability of
titles over images.
Update site screenshot