Muz.li should support Firefox with an extension. Especially now that Chrome is becoming the modern-day IE.

Does webflow have direct integration with sketch files?

This has been a fantastic response! Seeing that, surprisingly, there are many designers who code in this discussion––what do you use for a/b testing, lead generation, and other conversion technologies?

I am hoping to learn more about how people use landing page services, but didn't want to lead the question too much.

Tycho, Bonobo, Moderat. Seems like that music was made for designing. It doesn't hurt that Tycho is a veteran designer.

Zeplin has been a great company and inspired a lot of brand loyalty. With that said, Invision's fully integrated design deliverable system, and one less expense will ultimately win out.