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/matchers/DiffBuilder.js

@@ -1,12 +1,13 @@
 getJasmineRequireObj().DiffBuilder = function(j$) {
-  return function DiffBuilder() {
+  return function DiffBuilder(config) {
     var path = new j$.ObjectPath(),
-        mismatches = [];
+        mismatches = [],
+        prettyPrinter = (config || {}).prettyPrinter || j$.makePrettyPrinter();
 
     return {
       record: function (actual, expected, formatter) {
         formatter = formatter || defaultFormatter;
-        mismatches.push(formatter(actual, expected, path));
+        mismatches.push(formatter(actual, expected, path, prettyPrinter));
       },
 
       getMessage: function () {
@@ -21,12 +22,12 @@ getJasmineRequireObj().DiffBuilder = function(j$) {
       }
     };
 
-    function defaultFormatter (actual, expected, path) {
+    function defaultFormatter (actual, expected, path, prettyPrinter) {
       return 'Expected ' +
         path + (path.depth() ? ' = ' : '') +
-        j$.pp(actual) +
+        prettyPrinter(actual) +
         ' to equal ' +
-        j$.pp(expected) +
+        prettyPrinter(expected) +
         '.';
     }
   };

src/core/matchers/matchersUtil.js

@@ -45,7 +45,7 @@ getJasmineRequireObj().MatchersUtil = function(j$) {
         if (i > 0) {
           message += ',';
         }
-        message += ' ' + j$.pp(expected[i]);
+        message += ' ' + self.pp(expected[i]);
       }
     }
 

src/core/matchers/toEqual.js

@@ -14,7 +14,7 @@ getJasmineRequireObj().toEqual = function(j$) {
         var result = {
             pass: false
           },
-          diffBuilder = j$.DiffBuilder();
+          diffBuilder = j$.DiffBuilder({prettyPrinter: util.pp});
 
         result.pass = util.equals(actual, expected, diffBuilder);