Allow to pass encoded params.

[danhper]

I am trying to send a request with a query as follow:

http://example.com?foo[]=1&foo[]=2

which is to encode easy using Plug.Conn.Query.encode, as %{foo: [1, 2]} yields the correct result.
However, it seems to be impossible to pass an already encoded query to HTTPoison,
as URI.encode_query fails.
Of course, we can append directly to the URL, but as the params option already exists,
I think it would be nicer to support this case as well.

This patch keeps the previous behavior when the query is not a binary, and avoid
trying to reencode it when it is already a binary.

Thank you.

[edgurgel]

I'm not sure if this change is desirable. If you already encoded the query params why would you pass it to the params option? The only real "benefit" is that HTTPoison would add the ? right?

[danhper]

Sorry for the delay!

The only real "benefit" is that HTTPoison would add the ? right?

That would be one benefit, but for me the major benefit is to keep things consistent.
I often wrap my calls in the following way

defmodule MyHTTPClient do
  use HTTPoison.Base

  def get_something(query) do
    get("/path/to/something", [], params: query)
  end
end

and I would rather have HTTPoison do the right thing with my query
than handle it at the application level.