Backport exception handling fixes.

The recent changes to printing also required these fixes.

lib/pry.rb

@@ -21,7 +21,7 @@ class Pry
   DEFAULT_PRINT = proc do |output, value|
     stringified = begin
                     value.pretty_inspect
-                  rescue Exception => ex
+                  rescue RescuableException => ex
                     nil
                   end
 

lib/pry/pry_instance.rb

@@ -223,13 +223,13 @@ class Pry
     else
       print.call output, result
     end
-  rescue Exception => e
+  rescue RescuableException => e
     # Being uber-paranoid here, given that this exception arose because we couldn't
     # serialize something in the user's program, let's not assume we can serialize
     # the exception either.
     begin
       output.puts "output error: #{e.inspect}"
-    rescue Exception => e
+    rescue RescuableException => e
       if last_result_is_exception?
         output.puts "output error: failed to show exception"
       else