Add "Deploys by Netlify" badge to footer

[mattstratton]

Per Netlify, in order for devopsdays.org to continue being hosted for free, we will need to add a badge for Netlify to the site (this is due to the high amount of bandwidth we are using).

Code will look like this:

<a href="https://www.netlify.com">
  <img src="https://www.netlify.com/img/global/badges/netlify-light.svg"/>
</a>

Note - while normally I would recommend we self-host the image, given the bandwidth issue, we might as well use Netlify's origin instead of our own :)

[kmugrage]

Seems like a reasonable request

[bridgetkromhout]

while normally I would recommend we self-host the image, given the bandwidth issue, we might as well use Netlify's origin instead of our own

This is a tiny image, though. And I really don't like the idea of something not controlled by us being displayed on the front page. Not that I think they'd change the picture on us, but always in motion is the future.

Also, I'd prefer a transparent background:

The link itself is fine, as is the placement (it's in a good place for it).

[mattstratton]

The choices we have for the badge are located here:

https://www.netlify.com/press/

I am okay with hosting the image itself. We were requested to use one of their badges, so I don't want to modify the image.

[mattstratton]

I updated #670 to now host the image from our own site instead of Netlify. As I mentioned, we need to use one of their badges; the light one (see the Press link above) seemed the least obtrusive.