Sage 10.8 released

[Volker Braun]

The "master" git branch has been updated to Sage-10.7. As always, you can get the latest beta version from the "develop" git branch. Alternatively, the self-contained source tarball is at http://www.sagemath.org/download-latest.html

981d7d71a27 (tag: 10.8, github/master, github/develop) Updated SageMath version to 10.8
7262ca702f9 (tag: 10.8.rc3) Updated SageMath version to 10.8.rc3