Move DD code into its own directory (#6)

reference/tests/unit/utils/test_http.py

@@ -0,0 +1,16 @@
+from ddtrace.utils.http import normalize_header_name
+
+
+class TestHeaderNameNormalization(object):
+
+    def test_name_is_trimmed(self):
+        assert normalize_header_name('   content-type   ') == 'content-type'
+
+    def test_name_is_lowered(self):
+        assert normalize_header_name('Content-Type') == 'content-type'
+
+    def test_none_does_not_raise_exception(self):
+        assert normalize_header_name(None) is None
+
+    def test_empty_does_not_raise_exception(self):
+        assert normalize_header_name('') == ''