Switch property to be "ARRAY" typed instead of is_many.

In #36 @brummett suggested that this should be an `ARRAY` property instead of `is_many`.  He's right! The `is_many` approach is not performant--NYTProf indicates it's spending most of its time inside `Carp` generating stacktraces after a doomed attempt to load a module called "Text" on every line.  This changes it to an `ARRAY`, which NYTProf shows has similar performance to the version of the module that pre-dated the prior PR.

(The new place that tops the list `_strip_quotes`.  It may be worth exploring a more efficient way to handle that case--maybe make it optional?  The current implementation doesn't handle a quoted string that contains the delimiter, anyway.)