Inlined source maps add hidden size, causing confusion

[msafi]

In my webpack config I had devtool set to inline-source-map. So the inlined source maps were included in the final bundle.js. I didn't know that, so when Webpack Bundle Analyzer was telling me that the highest level code container in my bundle is 500KB but right above it the bundle.js size is 2MB, I was very confused.

It would be useful to help the user know what's going on in these cases.

[valscion]

This is similar to #235