Polymake.jl 0.5.4 released

Today Polymake.jl 0.5.4 has been released.

Diff since v0.5.3

Closed issues:

• Building Polymake.jl sometimes segfaults (#310)
• cannot precompile (#328)
• Signal handling (#330)

Merged pull requests:

• Add note on how to cite. (#334) (@lkastner)
• bump to 0.5.4, update jll versions (#335) (@benlorenz)