Be more permissive about what is accepted as whitespace in first line

RFC 7230 states:
    Although the request-line and status-line grammar rules require
    that each of the component elements be separated by a single SP
    octet, recipients MAY instead parse on whitespace-delimited word
    boundaries and, aside from the CRLF terminator, treat any form
    of whitespace as the SP separator while ignoring preceding or
    trailing whitespace; such whitespace includes one or more of the
    following octets: SP, HTAB, VT (%x0B), FF (%x0C), or bare CR.
    However, lenient parsing can result in security vulnerabilities
    if there are multiple recipients of the message and each has
    its own unique interpretation of robustness (see Section 9.5).
Merge pull request #22 from dstufft/robustness-extra-whitespace

Be more permissive about what is accepted as whitespace in first line