Revise building a release instructions

[peterjc]

Re: https://github.com/biopython/biopython.github.io/blob/master/wiki/Building_a_release.md aka https://biopython.org/wiki/Building_a_release

This will probably fall to me, but the website changes have knock on implications for doing a Biopython release - the uploads are now done via https://github.com/biopython/DIST to appear under https://biopython.org/DIST/ - and we should also report their checksums in the email and blog release announcements.

[peterjc]

I recently learnt there is a difference between the annotated tags and the lightweight tags we've been using as currently descripted in http://biopython.org/wiki/Building_a_release - e.g.

$ git tag biopython-166
$ git push origin master --tags

The alternative annotated tags created with git tag -a ... (or -s or -u for signed) where you also give a message (or use -m or -F to set the message).

This difference is important if we want to use git push --follow-tags (supported in git 1.8.3 onwards) which won't bother with lightweight tags.

Edit: See also https://stackoverflow.com/questions/4971746/why-should-i-care-about-lightweight-vs-annotated-tags