Silent failure when a template file does not exist

My old [node-ios7crypt](https://github.com/mcandre/node-ios7crypt/tree/7fe7aa864a500d1c98309aeaf32c214d28dfefe9) web app would silently crash when referencing mustache template files that did not exist. Would be nice if mustache caught this error before attempting to read from template files.
