Add type annotations (PEP 484) (#25)

setup.cfg

@@ -1,5 +1,33 @@
 [bdist_wheel]
 universal=1
 
+[mypy]
+python_version = 3.5
+
+# Dynamic typing
+disallow_subclassing_any = True
+disallow_any_generics = True
+
+# Untyped definitions and calls
+disallow_untyped_calls = True
+disallow_untyped_defs = True
+disallow_incomplete_defs = True
+check_untyped_defs = True
+disallow_untyped_decorators = True
+
+# None and Optional handling
+no_implicit_optional = True
+
+# Warnings
+warn_redundant_casts = True
+warn_unused_ignores = True
+no_warn_no_return = True
+warn_return_any = True
+warn_unreachable = True
+
+# Other strictness checks
+strict_equality = True
+no_implicit_reexport = True
+
 [pep8]
 max-line-length = 160