set curl headers to Accept-Version: 2.0

[dunagan5887]

This should return full urls for the listing href's, as opposed to relative url paths.

Will need to update the various methods that use the href's from the API calls to expect this, especially Reverb_ReverbSync_Helper_Data::updateObject()
Reverb_ReverbSync_Helper_Orders_View::getLinkToItemOnReverb()