Raise An Error If No Args Are Supplied for Esbuild

[kinson]

Overview

An exception is manually raised to prevent esbuild from hanging without explanation.

This is a duplicate of https://github.com/phoenixframework/esbuild/pull/47 with test fixes. It also addresses #49 .

[josevalim]

I was able to merge #47 with a similar change proposed here, thank you!