Ignore if isomiR has only mutations.
Ignore if isomiR has only mutations.

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

git-svn-id: 7b23463547cc0a1b218dcc761682eb55cda078b4@116702 bc3139a8-67e5-0310-9ffc-ced21a209358

lpantano/isomiRs