Add svn test data

Some of the svn test data isn't making it into the sdists which causes unittests to fail.  This change to MANIFEST.in fixes that.

In addition, the fact that the tests pass with just this change to the MANIFEST.in implies that setuptools/tests/svn17_example.zip isn't needed (possibly it was checked in in the tests/ directory instead of tests/svn_data )

This pull request does not delete that file as I wasn't sure about that.