Zend\Http\Header\HederInterface docblock seems incorrect

The current version of [modules/zend.http.headers.rst](https://github.com/zendframework/zf2-documentation/blob/75712afcc92a0e9042eb9810671c9cfc455717d2/docs/languages/en/modules/zend.http.headers.rst#zendhttpheaderheaderinterface-methods) documents the `Zend\Http\Header\HeaderInterface`'s `toString()` as returning the header line 

> in the form of "NAME: VALUE\r\n"

This seems to be inconsistent with the actual return values of the `Zend\Http\Header\*` classes. Which one of these is incorrect? Should `toString()` return the headers with a CR and NL at the end of them (as per the spec) or should these docs be updated?