Rename "vm" to "runtime" for clarity

lib/handlebars.js

@@ -6,7 +6,7 @@ module.exports = Handlebars;
 require("./handlebars/utils");
 
 require("./handlebars/compiler");
-require("./handlebars/vm");
+require("./handlebars/runtime");
 
 // BEGIN(BROWSER)
 

lib/handlebars/runtime.js

@@ -54,7 +54,7 @@ Handlebars.VM = {
     } else if(partial instanceof Function) {
       return partial(context, options);
     } else if (!Handlebars.compile) {
-      throw new Handlebars.Exception("The partial " + name + " could not be compiled when running in vm mode");
+      throw new Handlebars.Exception("The partial " + name + " could not be compiled when running in runtime-only mode");
     } else {
       partials[name] = Handlebars.compile(partial);
       return partials[name](context, options);