Escape html in titles

Fix for a bug @kaelig spotted where title attributes are not escaped e.g. http://m.guardian.co.uk/football/2013/jun/14/owen-coyle-wigan-athletic-manager

Aside: Found out whilst doing this that we do not seem to get the alt text from the content API instead using the caption as the alt text, but I can't work out why from looking at the code.