Summary:
Certain unusual queries, like `[-]`, could tokenize into a list which included the empty string.
This would then convert into a query for `... LIKE "%"` which just joins the entire table.
Instead: tokenize smarter; never return the empty token; add some test cases.
Test Plan: Ran unit tests. Queried for `[[blah blah]]`, saw a reasonable query come out the other end.
Reviewers: chad
Reviewed By: chad
Subscribers: 20after4
Differential Revision: https://secure.phabricator.com/D16888
