Fix failing unit test on Windows

test_xmlrpclib was failing with "can't pickle thread.lock objects" on Windows.
Other small issues were related to backslashes in paths and different line endings.

tests/unit/test_request.py

@@ -5,7 +5,7 @@ from vcr.request import Request, HeadersDict
 
 def test_str():
     req = Request('GET', 'http://www.google.com/', '', {})
-    str(req) == '<Request (GET) http://www.google.com/>'
+    assert str(req) == '<Request (GET) http://www.google.com/>'
 
 
 def test_headers():

tests/unit/test_vcr.py

@@ -147,7 +147,7 @@ def test_vcr_path_transformer():
         # and it should still work with cassette_library_dir
         vcr = VCR(cassette_library_dir='/foo')
         with vcr.use_cassette('test') as cassette:
-            assert cassette._path == '/foo/test'
+            assert os.path.abspath(cassette._path) == os.path.abspath('/foo/test')
 
 
 @pytest.fixture