Byte Order Mark included in fulfilled string from SystemLoader.fetch when executed in node

[jonoward]

When SystemLoader.fetch is executed on node, if the source file is UTF-8 and has a BOM, this is not stripped out by default (see nodejs/node-v0.x-archive#1918). This is causing an issue in systemjs-builder, when minification is enabled, and the plugin-text is used, as the BOM gets encoded, so you land up with strings like:

"\ufeff<div>hello</div>"

I'll submit a PR for this shortly

[guybedford]

@jonoward thanks again for this.