Adding truncation to football liveblogs

* Very rudimentary truncation

This is two fold - Football's requirements are pretty simple, and live blogs are being rehashed.

We can look at extending [`shouldTruncate`](https://github.com/guardian/frontend/compare/football-liveblog-truncation?expand=1#diff-78360b6b49c840a5052f32afe5da688cR18) to return a set of arguments for [`truncate`](https://github.com/guardian/frontend/pull/3912/files#diff-78360b6b49c840a5052f32afe5da688cR25) dependant on factors. This seemed like over engineering for now.

# Show me the simple truncation
![truncate](https://cloud.githubusercontent.com/assets/31692/2704805/48ebcd26-c474-11e3-9fa3-7d5528060df8.png)


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![TRUNK](http://www.ohmagif.com/gif/0811/elephant-trunk-stunt.gif)