Added support for custom object formatters

Custom object formatters allow users to customize how an object is
stringified in matcher failure messages. This can already be done by
adding a `jasmineToString` method to the objects in question. But
it's not always desirable or possible to do that, particularly when
objects of a given "type" do not inherit from a specific prototype.
For instance, suppose a web service returns a list of foos that are
deserialized from JSON, e.g.:

   { fooId: 42, /* more properties */ }

The only way to define `jasmineToString` on those is by writing code to
add it to each instance at runtime. But a custom object formatter can
recognize that the object it's looking at is a foo and format it
accordingly:

   jasmine.addCustomObjectFormatter(function(obj) {
      if (typeof obj.fooId !== 'number') {
            return undefined;
        }

        return '[Foo with ID ' + obj.fooId + ']';
    });

Unlike `jasmineToString`, custom object formatters are scoped to a
particular spec or suite and don't require any changes to the code
under test.

src/core/asymmetric_equality/ArrayContaining.js

@@ -25,8 +25,8 @@ getJasmineRequireObj().ArrayContaining = function(j$) {
     return true;
   };
 
-  ArrayContaining.prototype.jasmineToString = function () {
-    return '<jasmine.arrayContaining(' + j$.pp(this.sample) +')>';
+  ArrayContaining.prototype.jasmineToString = function (pp) {
+    return '<jasmine.arrayContaining(' + pp(this.sample) +')>';
   };
 
   return ArrayContaining;