Restore older SimpleOptions parsing behavior for values with spaces
Summary:
Previously, you could do name=blah blah blah. After the recent update, we require spaces to be quoted.
Instead, permit unescaped spaces in values but not in keys. This fixes some older memes from pre-escape times.
Test Plan: Ran unit tests.
Reviewers: vrana
Reviewed By: vrana
CC: aran
Differential Revision: https://secure.phabricator.com/D5161