4.1.0

CHANGES:

• Add an optional size limit to read_line (#32 @djs55)
• Redefine type error as private type of polymorphic variant (#32 @dinosaure)
• Restore compatibility with alcotest 1.4.0 (#33 @craigfe)
• Update to cstruct 6.0.0 API, remove use of deprecated Cstruct.len (#34 @hannesm)