`<%<` and `<:<` are deprecated/removed

The must be viewable constraints `<%<`/`<:<` , is no longer available. So, the
tutorial fails on Scala version 2.10.

Relevant StackOverflow post: http://stackoverflow.com/questions/14983705/getting-scala-type-bound-error-not-found-type

Signed-off-by: Rohan Jain <crodjer@gmail.com>