Update .gitignore for vim swap files.
https://bugs.webkit.org/show_bug.cgi?id=109252

Patch by Seulgi Kim <seulgikim@company100.net> on 2013-02-08
Reviewed by Dirk Pranke.

When opening the same files multiple with vim, vim creates a .*.sw[a-p]
file as the swap file.

* .gitignore:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142309 268f45cc-cd09-0410-ab3c-d52691b4dbfc