Add mailing list signup form to homepage

[ssmangoeater]

We need to start collecting people's emails. Let's add a subscribe form to the footer of the website. Here's the Mailchimp info:

<!-- Begin Mailchimp Signup Form -->
<link href="//cdn-images.mailchimp.com/embedcode/slim-10_7.css" rel="stylesheet" type="text/css">
<style type="text/css">
    #mc_embed_signup{background:#fff; clear:left; font:14px Helvetica,Arial,sans-serif; }
    /* Add your own Mailchimp form style overrides in your site stylesheet or in this style block.
       We recommend moving this block and the preceding CSS link to the HEAD of your HTML file. */
</style>
<div id="mc_embed_signup">
<form action="https://sharestake.us1.list-manage.com/subscribe/post?u=6cb6b636781c4fcc0b7cbccf1&amp;id=1e3ebab5ba" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" class="validate" target="_blank" novalidate>
    <div id="mc_embed_signup_scroll">
    <label for="mce-EMAIL">Subscribe for important updates</label>
    <input type="email" value="" name="EMAIL" class="email" id="mce-EMAIL" placeholder="email address" required>
    <!-- real people should not fill this in and expect good things - do not remove this or risk form bot signups-->
    <div style="position: absolute; left: -5000px;" aria-hidden="true"><input type="text" name="b_6cb6b636781c4fcc0b7cbccf1_1e3ebab5ba" tabindex="-1" value=""></div>
    <div class="clear"><input type="submit" value="Subscribe" name="subscribe" id="mc-embedded-subscribe" class="button"></div>
    </div>
</form>
</div>

<!--End mc_embed_signup-->

We can add it to the footer of the website, above the legal stuff:

The form and the "Subscribe" button can be styled like this (with the grey background):

[ssmangoeater]

@0knxwledge @exitonoff @sharedStake-dev

[exitonoff]

Mailing list signup added in https://github.com/SharedStake/SharedStake-ui/pull/85.