Fix -r,--header, that was passing headers after CRLF

The `-r` or `--header` feature was broken, as headers were sent *after* the last double CRLF.

Since this feature is broken, perhaps it was never used. I suggest we rename `-r` to `-H` to make it more `curl`-like.

programs/cleos/httpc.cpp

@@ -198,12 +198,12 @@ namespace eosio { namespace client { namespace http {
    request_stream << "content-length: " << postjson.size() << "\r\n";
    request_stream << "Accept: */*\r\n";
    request_stream << "Connection: close\r\n";
-   request_stream << "\r\n";
    // append more customized headers
    std::vector<string>::iterator itr;
    for (itr = cp.headers.begin(); itr != cp.headers.end(); itr++) {
       request_stream << *itr << "\r\n";
    }
+   request_stream << "\r\n";
    request_stream << postjson;
 
    if ( print_request ) {