Fix footer links

This addresses two issues:

* Core team link in footer led to a 404. 'people' page is the closest page I could find.
* Trailing whitespaces were used to separate footer links with surrounding texts. Use Slim leading and trailing whitespaces (`<` and `>`) instead. (this kind of thing is why I still prefer ERB; it looks ridiculous and silly to write such markups to construct a footer. )