Renaming to resource_cursor

Similar to https://github.com/gae-init/gae-init-upload/commit/2c7253d56180479d71db2d989f096bca35e6474e this PR proposes to use a `resource_cursor` within the `resource_list()` method.
Merge pull request #9 from mdxs/patch-1

Renaming to resource_cursor