Update implementation for expanding env variable
Update implementation for expanding env variable

Replace the naive version with python built-in ``os.path.expandvars``

kungfusheep/TypeScript-Sublime-Plugin,zhengbli/TypeScript-Sublime-Plugin,hoanhtien/TypeScript-Sublime-Plugin,RyanCavanaugh/TypeScript-Sublime-Plugin,fongandrew/TypeScript-Sublime-JSX-Plugin,fongandrew/TypeScript-Sublime-JSX-Plugin,kungfusheep/TypeScript-Sublime-Plugin,Microsoft/TypeScript-Sublime-Plugin,Microsoft/TypeScript-Sublime-Plugin,fongandrew/TypeScript-Sublime-JSX-Plugin,Microsoft/TypeScript-Sublime-Plugin,hoanhtien/TypeScript-Sublime-Plugin,hoanhtien/TypeScript-Sublime-Plugin,zhengbli/TypeScript-Sublime-Plugin,RyanCavanaugh/TypeScript-Sublime-Plugin,zhengbli/TypeScript-Sublime-Plugin,kungfusheep/TypeScript-Sublime-Plugin,RyanCavanaugh/TypeScript-Sublime-Plugin