Refactor: Simplify Enumerator Refinement

Why This Change Is Necessary
========================================================================

The [original PR][1] was submitted by @ronen and at the time I had not
looked into it sufficiently.  It seems as though this code can be
greatly simplified by leveraging the fact that we are already refining
an `Enumerator` and therefore there is no need to wrap in another
`Enumerator`.

What These Changes Do To Address the Issue
========================================================================

Remove the wrapping `Enumerator`

Caveats
------------------------------------------------------------------------

I'd love to have @ronen take a look at this and see if anything jumps
out as being very wrong about this implementation.

Side Effects Caused By This Change
========================================================================

None expected.

------------------------------------------------------------------------

**Relevant URLs:**

  * [Original PR Link][1]

------------------------------------------------------------------------

[1]: #126

Author: jfelchner

lib/ruby-progressbar/refinements/enumerator.rb

@@ -3,19 +3,15 @@ module Refinements
 module Enumerator
 refine ::Enumerator do
   def with_progressbar(options = {}, &block)
-    chain = ::Enumerator.new do |yielder|
-      progress_bar = ProgressBar.create(options.merge(:starting_at => 0, :total => size))
+    progress_bar = ProgressBar.create(options.merge(:starting_at => 0, :total => size))
 
-      each do |*args|
-        yielder.yield(*args).tap do
-          progress_bar.increment
-        end
-      end
-    end
+    each do |*yielded_args|
+      progress_bar.increment
 
-    return chain unless block
+      next unless block
 
-    chain.each(&block)
+      yield(*yielded_args)
+    end
   end
 end
 end