Debounce multiple rapid generateCode calls.

Fix for issue #218.
Changing compression level or on page load causes a large amount of generate code requests as each source file is loaded. Because there's no guarantee the order that these requests will start-and more importantly, end-the generated code can contain undefined code snippets.

"Debounce" multiple `generateCode` calls by delaying the call, and extending this out as each rapid request comes in.