Fix SCM link in readme

[zmoon]

I also found a few old links that don't work that could be updated if want:

• http://www.rtweb.aer.com/
• https://www.jcsda.noaa.gov/documents/meetings/wkshp2008/4/JCSDA_2008_Li.pdf

AER has a new website (https://www.aer.com/) and the presentation can be found with Wayback Machine (http://web.archive.org/web/20170508024706/https://www.jcsda.noaa.gov/documents/meetings/wkshp2008/4/JCSDA_2008_Li.pdf)

[zmoon]

It would be helpful for visitors to the repo/readme if this link were fixed.