v0.12.0

[CoffeeTableEspresso]

Breaking Changes:

• str->replace now returns a second value: the number of replacements done.
• echo can now print out a variable number of expressions.
• destructors for user data now require an extra parameter (the YASL_State *).
• Method look-ups now only look at the meta-table, not the object itself.

Improvements:

• Better error messages when a method is not found.

Bug Fixes:

• Fixed dangling pointer in closure upvalues, if closure was deleted before it could be closed.