better t.toIdentifier behaviour that doesn't camelcase on underscores - fixes #610

lib/6to5/types/index.js

@@ -226,7 +226,7 @@ t.prependToMemberExpression = function (member, append) {
 };
 
 /**
- * Description
+ * Check if the input `node` is going to be evaluated, ie. is a refernece.
  *
  * @param {Object} node
  * @param {Object} parent
@@ -331,13 +331,10 @@ t.toIdentifier = function (name) {
   name = name.replace(/^[-0-9]+/, "");
 
   // camel case
-  name = name.replace(/[-_\s]+(.)?/g, function (match, c) {
+  name = name.replace(/[-\s]+(.)?/g, function (match, c) {
     return c ? c.toUpperCase() : "";
   });
 
-  // remove underscores from start of name
-  name = name.replace(/^\_/, "");
-
   if (!t.isValidIdentifier(name)) {
     name = "_" + name;
   }