Add tools/vim to .gitignore.

TBR=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/51889004

Cr-Commit-Position: refs/heads/master@{#9237}
diff --git a/.gitignore b/.gitignore
index 4a6d211..9c328ec 100644
--- a/.gitignore
+++ b/.gitignore
@@ -146,6 +146,7 @@
 /tools/swarming_client
 /tools/tsan_suppressions
 /tools/valgrind
+/tools/vim
 /tools/win
 /tools/whitespace.txt
 /webrtc/examples/android/media_demo/bin