[SPARK-2788] [STREAMING] Add location filtering to Twitter streams

TwitterUtils.createStream(...) allows users to specify keywords that restrict the tweets that are returned. This change adds a location parameter that also restricts the returned tweets.
I didnt get you, why are you adding this this method? This does not have the locations. Instead isnt it better to keep the existing function as is and add 
```
 def createStream(
      ssc: StreamingContext,
      twitterAuth: Option[Authorization],
      filters: Seq[String],
      locations: Seq[String],
      storageLevel: StorageLevel
    ): ReceiverInputDStream[Status] = {
    createStream(ssc, twitterAuth, filters, Nil, storageLevel)
  }
```

Also worth remember that Scala does not allow two overloaded functions to have default params. That would give compiler errors.