Singular.jl 0.5.8 released

Today Singular.jl 0.5.8 has been released.

Diff since v0.5.7

Closed issues:

• n_unknown: ring or field (#170)
• Refactor convert_return_value (#338)
• The documentation for lift is wrong (#452)
• Coefficient ring not working for fq_nmod/fq (#467)

Merged pull requests:

• Update documentation with new links to AbstractAlgebra. (#460) (@wbhart)
• Bump version (#462) (@thofma)
• Lift (#464) (@hannes14)
• first try on immutables (#468) (@tthsqe12)
• split n_unknown into n_RingElem and n_FieldElem (#469) (@tthsqe12)
• Refactor convert return value (#470) (@tthsqe12)
• for better or worse cap characteristic to INT_MAX (#471) (@tthsqe12)
• Bump versions (#472) (@thofma)
• rename symbols as appropriate (#473) (@tthsqe12)