• Fixes Rename renderEpoxyHTML() #53 by renaming renderEpoxyHTML() to render_epoxy()
• Fixes Rename epoxyHTML() #52 by renaming epoxyHTML() to ui_epoxy_html()
• Also renames epoxy_output_mustache() to ui_epoxy_mustache()

I think it's important that render_ and ui_ come first, since there's strong precedent for renderThing() in Shiny. And if both ui_epoxy_ functions have consistent prefixes, I think render_epoxy() is a better name that's more consistent with applying to both.