fix(buffer): get_buf to not return consumed part of buffer

Closes #406

src/server/mod.rs

@@ -228,7 +228,6 @@ mod tests {
             Host: example.domain\r\n\
             Expect: 100-continue\r\n\
             Content-Length: 10\r\n\
-            Connection: close\r\n\
             \r\n\
             1234567890\
         ");