message: make-vector: don't require lvalues
diff: @@ -7,9 +7,9 @@ namespace elle
  {
  /// This is really the `map` function in functional languages:
  /// a vector of the values of `fun(e)` for e in c.
  - template <typename Container, typename Fun>
  + template <typename Cont, typename Fun>
  auto
  - make_vector(Container& c, Fun&& fun)
  + make_vector(const Cont& c, Fun&& fun)
  -> std::vector<decltype(fun(*c.begin()))> // SFINAE
  {
  using Res = decltype(fun(*c.begin()));
  