Fixes swagger-editor/#1502.

Change logic for markdown rendering to:

1. Convert source markdown to HTML
2. Sanitize HTML
3. Send sanitized HTML to markdown renderer

src/core/components/providers/markdown.jsx

@@ -1,37 +1,40 @@
 import React from "react"
 import PropTypes from "prop-types"
-import Remarkable from "react-remarkable"
+import Remarkable from "remarkable"
 import sanitize from "sanitize-html"
 
 function Markdown({ source }) {
-  const sanitized = sanitizer(source)
+    const html = new Remarkable({
+        html: true,
+        typographer: true,
+        breaks: true,
+        linkify: true,
+        linkTarget: "_blank"
+    }).render(source)
+    const sanitized = sanitizer(html)
 
-  // sometimes the sanitizer returns "undefined" as a string
-  if(!source || !sanitized || sanitized === "undefined") {
-    return null
-  }
+    if ( !source || !html || !sanitized ) {
+        return null
+    }
 
-  return <div className="markdown">
-    <Remarkable
-      options={{html: true, typographer: true, breaks: true, linkify: true, linkTarget: "_blank"}}
-      source={sanitized}
-      ></Remarkable>
-  </div>
+    return (
+        <div className="markdown" dangerouslySetInnerHTML={{ __html: sanitized }}></div>
+    )
 }
 
 Markdown.propTypes = {
-  source: PropTypes.string.isRequired
+    source: PropTypes.string.isRequired
 }
 
 export default Markdown
 
 const sanitizeOptions = {
-  textFilter: function(text) {
-    return text
-      .replace(/&quot;/g, "\"")
-  }
+    allowedTags: sanitize.defaults.allowedTags.concat([ "img" ]),
+    textFilter: function(text) {
+        return text.replace(/&quot;/g, "\"")
+    }
 }
 
 export function sanitizer(str) {
-  return sanitize(str, sanitizeOptions)
+    return sanitize(str, sanitizeOptions)
 }

src/core/components/response.jsx

@@ -111,7 +111,7 @@ export default class Response extends React.Component {
     if(examples) {
       examples = examples.map(example => {
         // Remove unwanted properties from examples
-        return example.set("$$ref", undefined)
+        return example.set ? example.set("$$ref", undefined) : example
       })
     }