Accumulate and Sublist exercises for Scala.

Hello,

I thought it would be nice to build up some additional exercises for Scala.  I completed all the exercises that are currently available for Scala, and thought I would pitch in and add some more. This pull request includes ports of the Accumulate and Sublist examples from Haskell. 

I will be more than happy to port some more over if these are useful. Let me know if you would like any changes to these. 

Best Regards,
Ric