Lint classes better (much better) --- Fixes gh-1940

So, so much better!
This empty branch threw me for a second--it looked like you had forgotten to issue an error here. I was going to point out that the branch isn't covered, but I think a better solution would be to remove it altogether:

```diff
-} else if (!isPropertyName(name)) {
-  // error --- class methods should be identifiers or strings.
-} else {
+} else if (isPropertyName(name)) {
   // Non-Computed PropertyName
```

What do you think?