Broken HTML image link in PR when using Danger

# Report

## What did you do?
Hello everyone. I'm trying to implement in my Danger file one very interesting thing. And everything works fine except the following:

I'm trying to add an image using HTML and I have to use HTML because I can't resize an image using Markdown on GitHub.

## What did you expect to happen?

Here's a line in Danger file:

`warn('')`

I also tried like this:

`warn(''.html_safe)`

## What happened instead?

Here what I get in PR comment

`<img src=https://docs.aws.amazon.com/images/aws_logo_105x39.png width="100">`

So instead of `<` and `>` i get `<` and `>` and my image isn't loaded.

## Your Environment

* Which CI are you running on?
Travis CI
* Are you running the latest version of Danger?
Yes

I'm looking forward to your answer.