adding sqlalchemy as a dependency

Author: Matt George

setup.py

@@ -10,7 +10,7 @@
     license="MIT",
     url='https://github.com/binarydud/redshift_sqlalchemy',
     packages=['redshift_sqlalchemy'],
-    install_requires=['psycopg2 >= 2.5'],
+    install_requires=['psycopg2 == 2.5', 'SQLAlchemy==0.8.0b2'],
     include_package_data=True,
     zip_safe=False,
     classifiers=[