Fix inconsistent formatting of emails in the README.
Link to nightly builds at the top of the README.
Link to nightlies now more prominent.
Link to nightlies now h3 instead of h4.
Readme nightlies link now h2 instead of h3.
Try to put nightly builds link in the h3 tag.

Let's see how this works.
Merge branch 'f-nighlies-readme' into develop