Update .gitignore

Ignore:
 * Intellij Idea directory
 * pem certificate files

Change-Id: I9b33552b7787b6460e027d6a6513d5e4ee566bbf
diff --git a/.gitignore b/.gitignore
index 00e1907..9965ad4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,5 @@
 gerrit.config
 secure.config
 replication.config
+.idea
+**/*.pem