Fix SQLAlchemy 1.2.0 compatibility (#411)

Author: Gr1N

Diff for: aiopg/sa/result.py

@@ -100,7 +100,12 @@ def __init__(self, result_proxy, metadata):
         self._keymap = keymap = {}
         self.keys = []
         dialect = result_proxy.dialect
-        typemap = dialect.dbapi_type_map
+
+        # `dbapi_type_map` property removed in SQLAlchemy 1.2+.
+        # Usage of `getattr` only needed for backward compatibility with
+        # older versions of SQLAlchemy.
+        typemap = getattr(dialect, 'dbapi_type_map', {})
+
         assert dialect.case_sensitive, \
             "Doesn't support case insensitive database connection"
 

Diff for: requirements.txt

@@ -11,5 +11,5 @@ pytest-cov==2.5.1
 pytest-sugar==0.9.0
 pytest-timeout==1.2.1
 sphinxcontrib-asyncio==0.2.0
-sqlalchemy==1.1.15
+sqlalchemy==1.2.0
 psycopg2==2.6.2