including numpy and GDAL as explicit requirements
as previous versions of django failed silently
when these weren't installed. with django >= 1.3
this throws an exception. the requirement of
libgdal and numpy is already outlined in README.
when the commit manually decorator is used, django
forces you to manage the transaction in all cases.
since we handle the GET case with a simple
response and no transaction commit, an exception
was being thrown. moving the transaction case to
the second part of the method resolves this.