Singular.jl 0.4.5 released

Here is an overview of the changes in this release of Singular.jl:

• Addition, subtraction, and multiplication in QQ now ensure that the result is reduced. This means that the strange behavior 1/2 + 3/2 = 8/4 should not be observed anymore.
• Various bugs in the wrapper code have been fixed. In particular numerators and denominators are now handled correctly and should not crash.
• Errors such as 1/0 do not leave the Singular kernel in an error state, and thus future calculations should not be poisoned anymore.
• Support for Singular’s orderings has been added: PolynomialRing(QQ, ["x", "y", "z", "t"], ordering = ordering_dp(2)*ordering_wp(2,3)) is the analogue of ring r = 0,(x,y,z,t),(dp(2),wp(2,3)).