Remove unused .subsection-collection .title style
Improve HTML

This commit:
- Removes the sentence explaining how to use the updates. Pretty sure that it is self explanatory especially in the wider context of the manual) and so we don't need this sentence to explain.
- Changes the tags used to mark up the notes. The original markup is good for longer explanations of changes but in reality change notes are rarely over four words long so using headers and paragraphs is a bit too much. This change employs a definition list instead. Based on even more mature projects with more comprehensive change notes I think this design will still work.
Fix up styles for updates page

Given the flexible and highly changable length of the change discriptions and the affected page names, in terms of layouts this is about as nice as we're going to get while still accommodating all text lengths. This commit adds some styling for updates lists and removes some (now unused) styles for the old updates presentation.
Reverse order of change notes

SO that the most recent notes are at the top of the document reverse the order of them.
Merge pull request #96 from alphagov/improve-updates-page

Improve updates page