Support for author string in package.json

Allows one to use `{%= author.name %}`, `{%= author.email%}` and/or `{%= author.url %}` whether they use the string format (`"Full Name <email> (url)"`) or object format (`{ "name" : "foo", "email" : "email@foo.com", "url" : "baz.com"}`) of the author data in package.json.