Ignore IntelliJ '.iml' project file (#2671)

diff --git a/.gitignore b/.gitignore
index ae7a95b..1291f31 100644
--- a/.gitignore
+++ b/.gitignore
@@ -49,6 +49,7 @@
 # IntelliJ
 .idea
 *.class
+*.iml
 
 # Ansible
 ansible/environments/docker-machine/hosts