list gems with known memory issues

thanks @srpouyet
closes #6

thanks @mic-kul
related to #4

README.md

@@ -1,9 +1,8 @@
 # A list of gems that have memory leaks
 
-Links to issues, pull requests or articles demonstrating memory leaks:
+Links to issues, pull requests or articles demonstrating memory leaks (gems are listed alphabetically):
 - [celluloid > 0.16.0, < 0.17.2](https://github.com/celluloid/celluloid/pull/678)
 - [grape < 0.2.5](https://github.com/ruby-grape/grape/pull/291#issuecomment-11725614)
-- [newrelic_rpm < 3.9.8](https://discuss.newrelic.com/t/client-using-large-amount-of-memory/9307)
 - [oj < 2.12.4](https://github.com/ohler55/oj/issues/229)
 - [redcarpet < 3.3.3](https://github.com/vmg/redcarpet/pull/516)
 - [sidekiq < 3.5.1](https://github.com/mperham/sidekiq/pull/2598)
@@ -12,6 +11,16 @@ Links to issues, pull requests or articles demonstrating memory leaks:
 
 Your Ruby app leaks memory if you see gems above in your _Gemfile.lock_. The list above may save you a week or more of your personal life.
 
+# A list of gems that have memory issues (but not actual leaks)
+
+It appears some contributors submit gems with known memory issues, but not actual leaks. While those issues don't qualify as leaks they may still be important. I prefer listing them here to help other developers rather than just hiding them.
+
+Links to known memory issues (gems are listed alphabetically):
+- [axlsx](https://github.com/randym/axlsx/issues/276)
+- [delayed_job >= 4.06](https://github.com/collectiveidea/delayed_job/issues/776)
+- [newrelic_rpm >= 3.9.4, <= 3.9.7](https://discuss.newrelic.com/t/client-using-large-amount-of-memory/9307)
+
+
 # Contributing
 Feel free to submit a PR if you find any memory leaks in gems.
 The format is the following:
@@ -22,4 +31,6 @@ Thanks!
 # Contributors
 - [Graham Conzett @conzett](https://github.com/conzett)
 - [Jacob Oakes @oakesja](https://github.com/oakesja)
-- [Ilya Vassilevsky](https://github.com/vassilevsky)
+- [Ilya Vassilevsky @vassilevsky](https://github.com/vassilevsky)
+- [Sebastiaan Pouyet @srpouyet](https://github.com/srpouyet)
+- [Michal Kulesza @mic-kul](https://github.com/mic-kul)