Allow SimpleOptions to parse quoted keys and values

Summary:
Ref T2574. Currently, the SimpleOptions format seems pretty good for use in Remarkup, but does not permit characters like "," and "=" to be included in strings.

Allow keys or values to be quoted, so inputs like name="Bartholemew, High Lord of Ravnica" are parseable.

Test Plan: Expanded unit test coverage.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Maniphest Tasks: T2574

Differential Revision: https://secure.phabricator.com/D5047