Implement fetchAll

[ZanGOlie]

I'm using this library in a situation where I have to make multiple calls to an API. I would typically use UrlFetchApp.fetchAll in such situations, but since I need to use this library's fetch method, I have to resort to making calls in series which will drastically increase execution time and eventually exceed the run-time limits.
A fetchAll method for this library would be essential for such situation.