Remove timeago prefixes on pt-BR translations

Redundant occurrences of timeago prefixes and suffixes
![Selection_038](https://f.cloud.github.com/assets/1200033/241325/ba6ca274-89a4-11e2-9ee1-da4dba261713.png)

Just like what happens in English language, in Portuguese there's no need to repeat the prefix / suffix. Indeed, this wrong behavior causes a bad impression about Diaspora pt-BR translations -- at most because the timeago strings appear almost everywhere on feeds.

An analog wrong string in English would be: `ago less than a minute ago`.