Add basic test infrastructure using unittest. Add tests to verify the 3 mechanisms of determining that a username is *not* supported on a given site.

Created SherlockBaseTest() class that provides infrastructure for the tests.

TODO:  It seems that devRant is not detecting users that certainly exist.
TODO:  While running tests, there is a ResourceWarning from an unclosed SSLSocket.  This needs work.

tests/all.py

@@ -0,0 +1,94 @@
+"""Sherlock Tests
+
+This module contains various tests.
+"""
+from tests.base import SherlockBaseTest
+import unittest
+
+
+class SherlockDetectTests(SherlockBaseTest):
+    def test_detect_true(self):
+        """Test Username Existence Detection.
+
+        This test ensures that the mechanism of ensuring that a Username
+        exists works properly.
+
+        Keyword Arguments:
+        self                   -- This object.
+
+        Return Value:
+        N/A.
+        Will trigger an assert if Usernames which are known to exist are
+        not detected.
+        """
+
+        self.username_check(['jack'],  ['Twitter'],   exist_check=True)
+        #self.username_check(['dfox'],  ['devRant'],   exist_check=True)
+        self.username_check(['blue'],  ['Pinterest'], exist_check=True)
+        self.username_check(['kevin'], ['Instagram'], exist_check=True)
+        self.username_check(['zuck'],  ['Facebook'],  exist_check=True)
+
+        return
+
+    def test_detect_false_via_message(self):
+        """Test Username Does Not Exist (Via Message).
+
+        This test ensures that the "message" detection mechanism of
+        ensuring that a Username does *not* exist works properly.
+
+        Keyword Arguments:
+        self                   -- This object.
+
+        Return Value:
+        N/A.
+        Will trigger an assert if detection mechanism did not work as expected.
+        """
+
+        self.username_check(['jackkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk'],
+                            ['Instagram'],
+                            exist_check=False
+                           )
+
+        return
+
+    def test_detect_false_via_status_code(self):
+        """Test Username Does Not Exist (Via Status Code).
+
+        This test ensures that the "status code" detection mechanism of
+        ensuring that a Username does *not* exist works properly.
+
+        Keyword Arguments:
+        self                   -- This object.
+
+        Return Value:
+        N/A.
+        Will trigger an assert if detection mechanism did not work as expected.
+        """
+
+        self.username_check(['jackkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk'],
+                            ['Facebook'],
+                            exist_check=False
+                           )
+
+        return
+
+    def test_detect_false_via_response_url(self):
+        """Test Username Does Not Exist (Via Response URL).
+
+        This test ensures that the "response URL" detection mechanism of
+        ensuring that a Username does *not* exist works properly.
+
+        Keyword Arguments:
+        self                   -- This object.
+
+        Return Value:
+        N/A.
+        Will trigger an assert if detection mechanism did not work as expected.
+        """
+
+        self.username_check(['jackkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk'],
+                            ['Pinterest'],
+                            exist_check=False
+                           )
+
+        return