Add default value setting for Configuration provider

src/dependency_injector/providers.pyx

@@ -667,15 +667,20 @@ cdef class Configuration(Provider):
         print(config.section1.option2())  # 2
     """
 
-    def __init__(self, name):
+    def __init__(self, name, default=None):
         """Initializer.
 
         :param name: Name of configuration unit.
         :type name: str
+
+        :param default: Default values of configuration unit.
+        :type default: dict
         """
         self.__name = name
         self.__value = None
         self.__children = dict()
+        if default is not None:
+            self.update(default)
         super(Configuration, self).__init__()
 
     def __deepcopy__(self, memo):

tests/unit/providers/test_configuration.py

@@ -60,6 +60,21 @@ class ConfigTests(unittest.TestCase):
         self.assertEqual(abc(), 1)
         self.assertEqual(abd(), 2)
 
+    def test_providers_with_default_value(self):
+
+        self.config = providers.Configuration(
+            name='config', default={'a': {'b': {'c': 1, 'd': 2}}})
+
+        a = self.config.a
+        ab = self.config.a.b
+        abc = self.config.a.b.c
+        abd = self.config.a.b.d
+
+        self.assertEqual(a(), {'b': {'c': 1, 'd': 2}})
+        self.assertEqual(ab(), {'c': 1, 'd': 2})
+        self.assertEqual(abc(), 1)
+        self.assertEqual(abd(), 2)
+
     def test_value_of_undefined_option(self):
         self.assertIsNone(self.config.a())