Complete TDD-based unit tests

Fixes Issue #1 by ensuring the BloomFilter.Size() probabilistic-based test clears.

- [x] Is it mergable?
- [ ] Did it pass the tests on Windows, Excel 2003?
- [ ] Did it pass the tests on Windows, Excel 2007?
- [ ] Did it pass the tests on Windows, Excel 2013?
- [ ] Did it pass the tests on Mac, Excel 2011?
- [ ] Was a spellchecker run on the source code and documentation after changes were made?