gitignore: ignore build products and file left by editors

BUG=chromium-os:17977
TEST=I've been using this for a few days without issue

Change-Id: Ib8e64bd5b59dff858a42214325bd9ab63db321ca
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d49952f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+._*
+.deps/*
+html/*
+obj/*
+test