Add example for using clj-time for current-date

Some people prefer to use the Joda-Time objects instead of
Java's Date objects for dealing with dates and times.

Provide an example in the description of how one can use clj-time
to interact with Joda-Time objects in addition to the solution
that covers Java Date objects.
Prefix return results with ;;->

Allow for copy/pasting into the repl, as well as align with output
from other examples in the book.
Remove leading => on examples

Allow for copy/pasting into the REPL, as well as match other code
excerpts in the book.
Edits to using clj-time to get current date
Merge pull request #253 from stevenproctor/current-date-clj-time

Add example of using clj-time to description of the current-date recipe