Singular.jl 0.18.13 released

Today Singular.jl 0.18.13 has been released.

Diff since v0.18.12

Closed issues:

• Reduce elements of QuotientRing modulo ideal (#691)

Merged pull requests:

• iszero and == for spoly in quotient ring (#703) (@hannes14)
• Version 0.18.13, update to latest libsingular_julia_jll (#704) (@fingolfin)