Improve JSON and Float docs

Author: josevalim

lib/elixir/lib/float.ex

@@ -577,15 +577,9 @@ defmodule Float do
  Returns a charlist which corresponds to the shortest text representation
  of the given float.
 
- The underlying algorithm changes depending on the Erlang/OTP version:
-
- * For OTP >= 24, it uses the algorithm presented in "Ryū: fast
- float-to-string conversion" in Proceedings of the SIGPLAN '2018
- Conference on Programming Language Design and Implementation.
-
- * For OTP < 24, it uses the algorithm presented in "Printing Floating-Point
- Numbers Quickly and Accurately" in Proceedings of the SIGPLAN '1996
- Conference on Programming Language Design and Implementation.
+ It uses the algorithm presented in "Ryū: fast float-to-string conversion"
+ in Proceedings of the SIGPLAN '2018 Conference on Programming Language
+ Design and Implementation.
 
  For a configurable representation, use `:erlang.float_to_list/2`.
 

lib/elixir/lib/json.ex

@@ -328,6 +328,12 @@ defmodule JSON do
  The second argument is a function that is recursively
  invoked to encode a term.
 
+ > #### IO and performance {: .tip}
+ >
+ > If you need to encode data to be sent over the network
+ > or written to the filesystem, consider using the more
+ > efficient `encode_to_iodata!/2`.
+
  ## Examples
 
  iex> JSON.encode!([123, "string", %{key: "value"}])