Upgrade to later version of Lua

[whitelizard]

Support for Lua 5.4 would be very nice indeed.

5.1 is rather old now?

[aw-engineer]

Support for lua 5.4 is currently blocked by:

• #23
• #24

Based on the unit test coverage results (#26) the scope of changes may be limited to just a few files, for core state machine functionality.

However, there may be additional work discovered as the tickets above are addressed