* Location, error formatting and stack trace improvements
* Static context for AST nodes
* Thunks no longer need `name`
* Prototype for showing snippets in error messages (old format still
available)
* Use ast.Function to represent methods and local function sugar.
* Change tests so that the error output is pretty
Fix a bunch of bugs:
- Reverse meaning of boolean argument to objectFieldsEx and objectHasEx
- Slice desugaring using `std.slice` instead of `slice` as a field name.
Support + on string and something else.
Support + on arrays
assertEqual should now work properly
