Updated the roadmap. Added the utilities.py module with Identities() which will be able to give retrogrades, inverses and inverse-retrogrades.
Added the Identites.retrograde() to utilities.py, Fixed typo, and added import of utilities.py in moebiusLib.py.
In utilities.py, made methods in Identity(): original(), retrograde(), inverse(), retrogradeInverse(). Wrote docstring for transposition()
Coded Identities.transposition() and fixed documentation details in utilities.py. Added notice of code used in cascaBell to README.md
Used Identities() as superclass of Progression, so that the class has identity methods available.
Merge pull request #5 from elerno/master

Started working on stage 2 of the roadmap.