Parsing improvements for strings and dates

I'm using your library to extract data from the Things app, so I encountered some issues with the output parser:

The strings returned from osascript may contain literal newlines and tab characters. Maybe some other whitespace characters, too.
In some cases simple string values are returned without quotes; sometimes there's a string value that has quotes in it, but it's still not quoted (see the tests for an example).
The date format returned from osascript isn't guaranteed to be parseable by Javascript, so you're left with an Invalid date and nothing to work off; I added a fallback that returns the original unparsed string in such cases.

Fixes and tests are below.

Thanks for making the parser!

FWeinb / node-osascript