constructor of stubbles\webapp\response\WebResponse now accepts correct http version strings only according to RFC 7230
ensure only http response with major version other than 1 receive a 505
add note about case sensitivity of header names
change stubbles\webapp\response\format\Formatter::format() to receive stubbles\webapp\response\Headers as second parameter
fix bug: response should not add content length header automatically when already added before
remove uselss import