Initial Commit
Change Exercise 4 from Array to ArraySeq

As of Scala 2.8, Array functors are no longer covariant and require an
implicit ClassManifest or ClassTag to infer the type of the Array.
Introducing such an implicit would break the type signature, so to keep
in the spirit of the exercises, I decided to convert this to an
ArraySeq.
Implement Exercises 1 through 4

These are the simpler Functor exercises . . .
Implement Exercise 5