Add template.cpp to gitignore.

It is generated experimental/webtry/build script, not checked-in the
source tree.

BUG=None
TEST=git status do not show it anymore as untracked file.
R=humper@google.com

Review URL: https://codereview.chromium.org/647633002
diff --git a/.gitignore b/.gitignore
index 32a7cf1..b8d31f3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,6 +10,7 @@
 TAGS
 bower_components
 common
+experimental/webtry/templates/template.cpp
 experimental/webtry/webtry.db
 gyp/build
 out