Fixes to setup.py

Use exec(open()) instead of execfile() to read in the version script.
It should now work on all versions of python.

Author: mmellison

setup.py

@@ -9,7 +9,8 @@
     pass
 
 # Version Information
-execfile('eve_mongoengine/__version__.py')
+# (Using 'execfile' is not version safe)
+exec(open('eve_mongoengine/__version__.py').read())
 VERSION = get_version()
 
 extra_opts = dict()