Have git ignore ".swp" files.

BUG=

Review URL: https://webrtc-codereview.appspot.com/1210005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3678 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/.gitignore b/.gitignore
index ff7a557..57ff375 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,6 +24,7 @@
 *_proto_cpp.xml
 *~
 .*.sw?
+.sw?
 .DS_Store
 .cproject
 .gdb_history