Avoid discarting isomiRS that only have mutations.
Avoid discarting isomiRS that only have mutations.

From: Lorena Pantano <lorena.pantano@gmail.com>

git-svn-id: 53622c1798e229c2bf592ed9ead8bb8a56616a54@116676 bc3139a8-67e5-0310-9ffc-ced21a209358

lpantano/isomiRs