Don't modify Thread.abort_on_exception

Closes #332.

lib/twitter/core_ext/enumerable.rb

@@ -1,23 +1,11 @@
 module Enumerable
 
   def threaded_map
-    abort_on_exception do
-      threads = []
-      each do |object|
-        threads << Thread.new { yield object }
-      end
-      threads.map(&:value)
+    threads = []
+    each do |object|
+      threads << Thread.new { yield object }
     end
-  end
-
-private
-
-  def abort_on_exception
-    initial_abort_on_exception = Thread.abort_on_exception
-    Thread.abort_on_exception ||= true
-    yield
-  ensure
-    Thread.abort_on_exception = initial_abort_on_exception
+    threads.map(&:value)
   end
 
 end