[WIP] Implement ConfigScopeCommentSource
Add on_enter and on_leave spec to traverse
Implement ScopePlugin
Note func-range behavior
Constantize scope tree key
Enable ScopePlugin
Merge branch 'scope-comment-config'

Conflicts:
	vint/ast/parsing.py
	vint/linting/linter.py
Merge branch 'master' of github.com:kuniwak/vint into implement-policies