Term needs more tests to document expected behavior, especially when value is a Resource

Created by: dchandekstark

Some methods of Term (at least in v0.2.3), such as #empty_property and #set do not appear to work properly when a Term value is a Resource. For example, #empty_property only removes the statements having the term predicate rather than the values of the terms (the resources). However, since neither the code not spec tests document the expected behavior I can't be sure this is bug.