Added persistent action to wikipedia suggest which shows the summary of a topic

This change adds a persistent action to the wikipedia suggest source, so you can look up a quick summary of a topic by simply invoking the persistent action (C-z) on the candidate. This way you do not even have to leave Emacs if you want get only a quick definition or info on a topic (e.g. when a person was born, etc.) and using persistent action you can easily get summaries of the interesting search candidates without leaving the search.

The info is fetched using the wikipedia api and formatted for readability. It even handles redirects, so e.g. if you search for jlaw then it will fetch info for Jennifer Lawrence.