Update news block to include the signup link

[mirie]

Please update the style prototype to include the newsletter signup text and link:

http://nyc-camp.github.io/2015/style-guide/#/components?id=masthead

Also, the nesting of the tags is not ideal. I think that buttons are supposed to be used inside of form. Also <a> should not wrap <button>. You can resolve this by simply using <a> and using a css class to style the link to look like a button.