Remove $item as constructor argument

Also, remove all methods using $item.

Class and methods are to be generic, and request body is to be
built in external code.

Leave in test_request for now at least
Merge branch dev into master
Updated documentation
Updated eBay_API_Call documentation
New method package_info()

Returns an array containing weight, dimensions, and other data.
Get package info from database using package_info()
test_request data now set using variables