Pull async matchers out to their own functions

- Makes AsyncExpectation closer to Expectation

src/core/matchers/requireAsyncMatchers.js

@@ -0,0 +1,16 @@
+getJasmineRequireObj().requireAsyncMatchers = function(jRequire, j$) {
+  var availableMatchers = [
+      'toBeResolved',
+      'toBeRejected',
+      'toBeResolvedTo',
+      'toBeRejectedWith'
+    ],
+    matchers = {};
+
+  for (var i = 0; i < availableMatchers.length; i++) {
+    var name = availableMatchers[i];
+    matchers[name] = jRequire[name](j$);
+  }
+
+  return matchers;
+};