Fix carousels

[jtojnar]

We often use images with varying dimensions in our carousels which is not supported by twbs atm so we are using some hacks (e.g. adding style attribute with dimensions of the largest image). We should investigate if there is a cleaner solution.

• http://kenwheeler.github.io/slick/
• http://owlgraphic.com/owlcarousel/
• http://flickity.metafizzy.co/ recommended by http://mediatemple.net/blog/tips/carousels-dont-have-to-be-complicated/