Added InvertedIndexInterface which InvertedIndexBuilder implements, and renamed weight to termWeight for clarity
Added IndexWriter class with tests for clearDirectory method which would clean up the directory after each test
Added clearDirectory code
Added tests for writeIndexWord
Moved NoSuchWordException to InvertedIndexInterface
Fixed bug in IndexedDocument.equals, added code for writeIndexWord, and fixed tests
Moved code to deserialise and check indexed document lists into a separate function
Added tests for writeIndex
Moved clearDirectory into IndexWriter (because it will need to use it, and for a lack of a better place to put it for now)
Added code for writeIndex and fixed test