No match stats unless match correctly tagged as football

Fix for key events overlap on football live blogs that haven't got the football/football tag. 
Now changed so that match stats don't show unless the live blog is correctly tagged as football.

Example of problem: http://www.theguardian.com/football/live/2014/oct/11/brazil-argentina-live-friendly-beijing

![screen shot 2014-10-13 at 10 54 37](https://cloud.githubusercontent.com/assets/2236852/4611822/f79eee9c-52be-11e4-8a96-668eafac582f.png)

cc @rich-nguyen 

slim chance, but this will also match a keyword like `foo-football/football-bar`

safer to split on `,` first (also `0` is a return value if found at the beginning, i.e. valid)

```config.page.keywordIds.split(',').indexOf('football/football') > -1```