Global Handlebars.compile uses its env

The basic strategy is that there will be a global Handlebars object for
the browser build, and that object will have a `compile` on it which
uses its environment in the compiler.

It will also be possible to glue things together manually by using the
AMD build and passing the environment to `compile` directly. Some of
these details are TBD.

lib/handlebars.js

@@ -20,7 +20,11 @@ var create = function() {
   hb.SafeString = SafeString;
   hb.Exception = Exception;
   hb.Utils = { extend: extend, escapeExpression: escapeExpression, isEmpty: isEmpty };
-  hb.compile = compile;
+  hb.compile = function(input, options) {
+    options = options || {};
+    options.env = options.env || env;
+    return compile(input, options);
+  };
   hb.precompile = precompile;
   hb.template = template;
   hb.createFrame = createFrame;