Allow version numbering of @imported less files so as to enabled browser cache busting when versions change.

...oaded by the browser so that you can bust the browser cache with a version number. Use like so: new(less.Parser)({suffix: '?version=12345'});

We're using less.js at Ning to recompile individual social networks' css when network owners change style paramerters.  This makes it so they can see a live update of what the changes to their color scheme, etc. will look like.  For this purpose, we _want_ a browser to cache the less files so that it's speedy to compile something with a lot of imports.  But we also want to be able to _bust_ that cache when we change the less styles so they don't get an old version of the less to customize.  So we added in this suffix parameter to less.js to let us do that.  Now we can still cache @import files on the users' browser, but bust the cache by updating the suffix when we make changes.