Patch by Tojiro@gmail.com and czambran@gmail.com for issue (#99)

Allows order_by on annotated field names not in the database.

https://code.google.com/p/django-pyodbc/issues/detail?id=99
attempted to bring up to speed with 1.6 but still get error on line 195 in compiler.py `if column.endswith("AS [%s]" % alias_name):` AttributeError: "list" object has no attribute "endswith"
take lionheart/master compiler.py
try/except import pytz
Merge pull request #63 from hobson/master

add missing `import pytz`