fix specs so that they work with mail v2.5.4

See also https://github.com/savonrb/savon-multipart/issues/10 and https://github.com/savonrb/savon/issues/569

Having looked through the change that broke the specs in Mail https://github.com/Aalanar/mail/commit/47438827f100fc26ce2218c205860d3dfb64f85a, the only difference in the split regexp is that it now contains `crlf` or `\n\r`. I tested some live SOAP responses and sure enough they call contain `crlf` instead of `\n` so I just updated the fixtures to use `crlf` line endings instead of `\n`.

The only other change that was required was to strip the extra `\n` that savon leaves in the returned response in the spec.