Remove mustache.to_html() (#735)

In the spirit of keeping the public API of mustache.js as small as
possible for maintainence reasons, the undocumented and un-tested
`.to_html()` method is removed.

The functionality involved, where it can rather invoke an optional
function provided with the result of `.render()`, instead of returning
it as a string like `.render()` does, is something that using projects
very easily can do themselfs -- it does not have to be provided by
mustache.js.

Author: phillipj

mustache.js

@@ -672,7 +672,6 @@
     escape: undefined,
     parse: undefined,
     render: undefined,
-    to_html: undefined,
     Scanner: undefined,
     Context: undefined,
     Writer: undefined,
@@ -727,20 +726,6 @@
     return defaultWriter.render(template, view, partials, tags);
   };
 
-  // This is here for backwards compatibility with 0.4.x.,
-  /*eslint-disable */ // eslint wants camel cased function name
-  mustache.to_html = function to_html (template, view, partials, send) {
-    /*eslint-enable*/
-
-    var result = mustache.render(template, view, partials);
-
-    if (isFunction(send)) {
-      send(result);
-    } else {
-      return result;
-    }
-  };
-
   // Export the escaping function so that the user may override it.
   // See https://github.com/janl/mustache.js/issues/244
   mustache.escape = escapeHtml;