Allow MustacheWriter to be called as a function with the view as the parameter.

For example, the documentation for Mustache.js shows the following:
var compiledTemplate = Mustache.compile(stringTemplate);
var templateOutput = compiledTemplate(templateData);

mustache/mustache-tests.ts

@@ -5,4 +5,7 @@ var output = Mustache.render("{{title}} spends {{calc}}", view);
 
 var person;
 var template = "<h1>{{firstName}} {{lastName}}</h1>Blog: {{blogURL}}";
-var html = Mustache.to_html(template, person);
+var html = Mustache.to_html(template, person);
+
+var writer = Mustache.compile(template);
+var writerOutput = writer(view);

mustache/mustache.d.ts

@@ -24,6 +24,7 @@ interface MustacheContext {
 }
 
 interface MustacheWriter {
+    (view: any): string;
     clearCache();
     compile(template: string, tags);
     compilePartial(name, template, tags);
@@ -42,6 +43,7 @@ interface MustacheStatic {
 
     parse(template: string, tags);
     clearCache(): MustacheWriter;
+    compile(template: string): MustacheWriter;
     compile(template: string, tags): MustacheWriter;
     compilePartial(name: string, template: string, tags): MustacheWriter;
     compileTokens(tokens, template: string): MustacheWriter;