fixed factor product [fixes #233]
Merge pull request #240 from ankurankan/dev

fixed factor product [fixes #233]
minor improvements in tests
minor improvements in tests [refs #241]
fixed factor_divide tests [fixes #241]
adds __truediv__ method to factors
adds test for truediv"
Merge pull request #242 from ankurankan/factor_divide

Factor divide
Merge remote-tracking branch 'upstream/dev' into issue224