[WIP] Hashes

- [x] obj = { prop1: 'val1', prop2: 'val2' }
- [x] some-prop: obj.prop
- [x] body { prop obj.prop } (won't fix)
- [x] obj['prop'] and obj['prop'] = 'val'
- [ ] obj.prop = 'val'
- [x] objects in `if`/`unless` and loops
- [x] for prop, value in obj
- [x] 'prop' in obj