FindMeFollowMe API - PUT fails (undefined findmefollow_del)

an attempted call to set FindMeFollowMe via the rest API fails, because the findmefollow_del function reports as undefined.

specifics:
a PUT to (server)/admin/api/api/rest/findmefollow/users/5136

fails with: 
```
{
"error":

{ "type": "Whoops\\Exception\\ErrorException", "message": "Call to undefined function FreePBX\\modules\\Findmefollow\\Api\\Rest\\findmefollow_del()", "file": "/var/www/html/admin/modules/findmefollow/Api/Rest/Findmefollow.php", "line": 45 }

}
```

this attempts to call findmefollow_del() here:
https://github.com/FreePBX/findmefollow/blob/release/15.0/Api/Rest/Findmefollow.php#L45

which fails, as findmefollow_del does not exist in findmefollowme class:
https://github.com/FreePBX/findmefollow/blob/release/15.0/Findmefollow.class.php