error: use of `format!` to build up a string from an iterator
  --> src/http.rs:50:17
   |
50 |       let brief = brief.lines()
   |  _________________^
51 | |         .skip(2)
52 | |         .take(num_lines - 4)
53 | |         .map(|l| format!("{}\n", l))
54 | |         .collect::<String>()
   | |____________________________^
   |
help: call `fold` instead
  --> src/http.rs:53:10
   |
53 |         .map(|l| format!("{}\n", l))
   |          ^^^
help: ... and use the `write!` macro here
  --> src/http.rs:53:18
   |
53 |         .map(|l| format!("{}\n", l))
   |                  ^^^^^^^^^^^^^^^^^^
   = note: this can be written more efficiently by appending to a `String` directly
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#format_collect
   = note: `-D clippy::format-collect` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::format_collect)]`