Add command line tool to compile Ace into HTML with Go template syntax

The main purpose of this command is making it easy to check an Ace template syntax.

The command takes a base template file and an inner template file as its arguments or if neither is specified, it reads STDIN and outputs the compile result to STDOUT. It also has formatted HTML output feature for readability. Now it doesn't execute Go template syntax, just displays it as is.

I hope it will be a start point for implementing command line tool at #31