fixed extension issue (issue #862 )

[lucianmat]

On file with multiple dots, extension is broken
Eg: on {ext:'.js'} myscript.prod.dust => myscript.js, instead it should
produce mysqcript.prod.js

[shama]

Thanks but closing as this is a duplicate of #856, #750, #625, #718, #730.

There's two ways ext could work; it could consider everything after the first dot the extension, or everything after the last dot the extension—it can't be smart enough to "guess" automatically. We chose the former because the use-case is more common (we encounter .min.js files all the time). That being said, you can use the rename option to specify a function that will use whatever custom naming logic you need.

FWIW, I believe support for this way was added in globule which will eventually get upstreamed into grunt.

[tkellen]

This has been resolved with the extDot option. See:
http://gruntjs.com/configuring-tasks#building-the-files-object-dynamically