Add some untracked directories to gitignore.
(Landing https://codereview.appspot.com/6488100/ for tfarina)



git-svn-id: http://skia.googlecode.com/svn/trunk@5507 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..895cc0c
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/out/
+/third_party/externals/