Add .gitignore.

Test: Don't see these files in git.
Change-Id: I78fe68d1e39a05ab4897315b8738faaaa84cff49
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..99cf5ff
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.*~