Dead link for 'Combine Archive' in the README

[yurivict]

No description provided.

[fbergmann]

the old combine.org server went down yesterday, and while a new server took up some of the load not all the links are present there yet. I'm not sure i should change it just yet. if you want to learn more about combine archives:

• https://bmcbioinformatics.biomedcentral.com/articles/10.1186/s12859-014-0369-z
• https://cat.bio.informatik.uni-rostock.de

I'll give the combine coordinators a bit more time to get things settled before changing the link.