Strip leading/trailing whitespace from search
Strip excess interstitial whitespace from search
Change Title filter to filter on many fields
Edition.internal_search looks at part titles
Whitespace
Edition.internal_search looks at bodies

This is something we may want to revert, depending on feedback from publisher
users.
Move regexification into Edition.internal_search

Using a regex is an implementation detail of the search. If we were to use eg
elasticsearch, we would pass it a string. This also deduplicates the code.
Note what the `true` parameter to Regexp.new does.
Merge pull request #82 from alphagov/filtering_improvements

Filtering improvements