Support --data-raw

[jasonmccreary]

The --data-raw option takes some interpretation. The curl docs do not state that it is mutually exclusive from --data. From a quick tests, it seems curl merges the data when called with both --data and --data-raw.

With that said, the common use case for --data-raw seems to be independent. When passed alone, this is the exact data to send in the request payload.

This PR adds support for --data-raw to the specification above - parsing it as form data when mixed with --data or sending it as the raw body when used independently.

[jonnywilliamson]

Just looking at the output for "with-raw-data".

Doesn't the withBody method require 2 parameters?

// Illuminate/Http/Client/PendingRequest.php
    /**
     * Attach a raw body to the request.
     *
     * @param  string  $content
     * @param  string  $contentType
     * @return $this
     */
    public function withBody($content, $contentType)
    {
        $this->bodyFormat('body');

        $this->pendingBody = $content;

        $this->contentType($contentType);

        return $this;
    }

[jasonmccreary]

I thought it was optional based on the content type of the request. However, looks like it's not. I'll need to revisit this as I use withBody in two spots.