Fix body params format

[urbsny]

Hi, thank you for such a fantastic library.
I encountered #240 issue.

tryitout-3.0.2.js is checking hasFiles attribute is "0".

    if (form.dataset.hasfiles === "0") {
        body = {};
        setter = (name, value) => _.set(body, name, value);
    } else {
        body = new FormData();
        setter = (name, value) => body.append(name, value);
    }

But generated html has not "0" or "1"

<form id="form-POSTapi-v1-login" data-method="POST" data-path="api/v1/login" data-authed="0" data-hasfiles="" data-headers="{&quot;Content-Type&quot;:&quot;application\/json&quot;,&quot;Accept&quot;:&quot;application\/json&quot;}" onsubmit="event.preventDefault(); executeTryOut('POSTapi-v1-login', this);">

[shalvah]

Ah, thank you.