Call graphs are wrong -- don't respect namespaces

[matheger]

Using pyan3==1.1.1.

test1.py:

myfunc()

test2.py:

def myfunc():
    ...

results in the following call graph:

Which is, of course, catastrophically wrong, because test1 does not use the function from test2 (note the lack of imports). As I'm currently trying to untangle a codebase with this exact problem, this completely breaks pyan3 for me.