slightly adjust test regex for google books to get volumes of periodicals as multiple items
slightly adjust google books singleRe to detect multiple volumes of a periodical as multiples forums.zotero.org/discussion/27849/google-books-translator-not-seeing-other-issues-list-as-multiple/
add tests
Merge pull request #535 from adam3smith/googlebooks

Googlebooks -  slightly adjust google books singleRe to detect multiple volumes of a periodical as multiples