Added test for getRankedDocuments
Added test for DescendingRankComparer that will be used for sorting the list of ranked documents
Added comparator code
Added code for getRankedDocuments and fixed IDF calculation
Fixed return type of getAllNodes in TestTextRank
Added constructor for DocumentTerm and exception message for addIndexedDocument
Added ProcessedDocument(Type)
Added DocumentProcessor(Interface)
Added Indexer class to coordinate various parts of the indexing system
Added missing IndexWriter call to Indexer; moved ExistingValueException to InvertedIndexInterface; removed IllegalStateException in TextRank when SameNodeException is thrown (the input array still has duplicate words at that point).
Added a small integration test as a sanity check to ensure that the various indexer components fit together - and it passes.