4.0.1

This is a minor release that includes a number of changes:

• Avoid using SIZEOF_VOID_P by @wilfwilson in #803
• doc: allow manual compile without all deps by @james-d-mitchell in #810
• Bump libsemigroups -> v2.1.4 by @james-d-mitchell in #809
• Change http -> https by @fingolfin in #818
• Remove spurious dependency on libgmp by @fingolfin in #820
• Improve compatibility with GAP's MatrixObj project by @fingolfin in #819
• Better congruence lattices by @james-d-mitchell in #815
• Add more matrix generators by @flsmith in #822