Add additional title attributes to links for enhanced screen reader acce...

...ssibility.

Unfortunately, screen readers don't like links of the form <a><span>Link text here</span></a>, or especially <a><div class="somearea"></div><span>Link text here</span></a>. There's no way to guess the link text.

I added title attributes to a few links to make them slightly more accessible.

I think I've done what is needed to suggest deploying this PR to prose.io. I'd really appreciate it if it could be, since it helps some with accessibility.

Thanks.