fix(doc): Do not allow duplicate names to be created

While diagnosing an issue related to scoring, I discovered that WOF
records are sometimes created with duplicate name values. While the
pelias/model code can detect some of them (and more will be fixed with
pelias/model#132), we should fix this issue at
the source.

Here's an example of what a document might look like today, before this
PR:

```
{
  name: { default: [ 'Kansas City' ] },
  phrase: { default: [ 'Kansas City', 'Kansas City' ] },
  ...
}
```

This can be fixed by checking each potential alternate name against the
"primary" name value.

src/peliasDocGenerators.js

@@ -88,7 +88,9 @@ function setupDocument(record, hierarchy) {
     else {
       if (record.name_aliases.length) {
         record.name_aliases.forEach(alias => {
-          wofDoc.setNameAlias('default', alias);
+          if (alias !== record.name) {
+            wofDoc.setNameAlias('default', alias);
+          }
         });
       }
       if (record.name_langs) {