Twitter/Facebook/Tumblr count down characters is hidden by the picture of the post. Close #3956

#3956

Another pull request https://github.com/diaspora/diaspora/pull/3963

![Pantallazo](https://f.cloud.github.com/assets/1108789/122261/2b975724-6e42-11e2-8590-fd6a088a52a5.png)


Test => https://jauspora.com 
User: `test_jauspora` 
Pass: `test_jauspora`