Define class properties in class_instance instead of directly on the class
General code cleanup
Load third-party code first
Move default scope into a method to avoid running too soon
Predefine `System` to point to `Rip::Core::System` class
Remove commented code
Fix Rip::Core::Object#inherited_properties

(fingers crossed)
Rename Rip::Utilities::Scope#{new,nested_context}
Synthesize a class without getting into infinite loop
Stop creating a special node for interpolation

Just build AST with synthesized to_string()

"a#{b}c"
'a' + b.to_string() + 'c'
Parse interpolation in regular expression as regular expression concatenation

/a#{b}c/
/a/ + b.to_string().to_regular_expression() + /c/
WIP Core unit tests