Added missing testcode for TestIndexWriter and renamed Indexer to IndexReaderInterface
Added tests for IndexReader
Added tests for RetrievedDocument
Added functionality to RetrievedDocument to make tests pass
Added similarTo method to RetrievedDocument to compare weights stored within the documents
Added code for similarTo method
Added getters for address and weight in IndexedDocument
Added code for retrieveDocuments and fixed tests
Added code for IndexReader.getDocuments