Review broken links in documentation

[tripu]

README[.md] points to two URLs that seem broken:

• http://www.statslab.cam.ac.uk/~sret1/analog/
• http://www.hypermail.org/

Either remove those URLs, or find their current incarnation.

(There might be more broken links; I've looked at those in the README only.)

[Bossking444]

README[.md] points to two URLs that seem broken:

• http://www.statslab.cam.ac.uk/~sret1/analog/
• http://www.hypermail.org/

Either remove those URLs, or find their current incarnation.

(There might be open links; I've looked at those in the README only.)