RFC 4180 compliance and line endings

[jonmast]

The documentation advertises that this "respects RFC 4180 for the output CSV format", but as discussed in #27 the RFC specifies CRLF for line separators while this library defaults to LF.

The RFC indicates implementations will vary, but that they should "be conservative in what you do, be liberal in what you accept from others" so I'd interpret a writer that deviates from this to not be compliant.

I don't know how feasible changing the default would at this point, but I think at least adding a caveat to the documentation would be helpful.