When using EG in the browser, variables aren't scoped correctly

[davej]

The specific error I get (in JS) is:

"Uncaught TypeError: Identifier '$targ$0' has already been declared"

This is because the let variables leak out of the files and into the global context. I suggest that EG provide a param to wrap the code in an IIFE (or possibly make it default behaviour?).

This is only an issue when using ES6 mode (because babel converts let to var) when running in a browser (not an issue in node).

[davej]

Perhaps an easier alternative might be just to point people towards something like gulp-iife, if you'd prefer not to deal with this in EG.