Extractors will run!!

1. Wrote a wrapper for `DumpExtractionContext` that delegates everything to a Spark `Broadcast[DumpExtractionContext]` variable. Fixes #13 

2. Took Spark/RDD stuff out of the `DumpExtractionContext` implementation. No problems anymore. All extractors work. Fixes #9 . Of course, ignoring `InfoboxExtractor` for now.

Note: The pull request is to the **nildev** branch. Let me know what you think and I'll merge this into nildev.