Fix a number of outstanding issues:

* {{}} escape their contents, {{{}}} and {{& }} do not
* Add support in the parser, tokenizer and AST for partials
  with context (support is still not there in the runtime)
* Fix some inconsistencies with the old behavior involving
  the correct printing of null and undefined
* Add Handlebars.Exception
* Fixed an issue involving ./foo and this/foo
* Fleshed out helperMissing in the specs (this will be
  moved out into handlebars proper once registerHelper
  and registerPartial are added)

lib/handlebars/printer.js

@@ -71,7 +71,9 @@ Handlebars.PrintVisitor.prototype.mustache = function(mustache) {
 };
 
 Handlebars.PrintVisitor.prototype.partial = function(partial) {
-  return this.pad("{{> " + this.accept(partial.id) + " }}");
+  var content = this.accept(partial.id);
+  if(partial.context) { content = content + " " + this.accept(partial.context); }
+  return this.pad("{{> " + content + " }}");
 };
 
 Handlebars.PrintVisitor.prototype.STRING = function(string) {