Singular.jl 0.18.7 released

Today Singular.jl 0.18.7 has been released.

Diff since v0.18.6

Merged pull requests:

• mres/nres for smodule (#670) (@hannes14)
• add saturation2 (an alternative to saturation) (#673) (@hannes14)
• Homogenize wrt. weights of ideals (#675) (@hannes14)
• Bump versions of AA and Nemo (#676) (@thofma)