Deprecated the Promise config setting

4.0 will only support environments that have native promises, so there will
no longer be a need for a user-supplied promise library

spec/core/EnvSpec.js

@@ -399,11 +399,17 @@ describe('Env', function() {
     });
 
     it('can be configured with a custom library', function() {
+      spyOn(env, 'deprecated');
       var myLibrary = {
         resolve: jasmine.createSpy(),
         reject: jasmine.createSpy()
       };
       env.configure({ Promise: myLibrary });
+      expect(env.deprecated).toHaveBeenCalledWith(
+        'The `Promise` config property is deprecated. Future versions of ' +
+          'Jasmine will create native promises even if the `Promise` config ' +
+          'property is set. Please remove it.'
+      );
     });
 
     it('cannot be configured with an invalid promise library', function() {

spec/core/SpySpec.js

@@ -271,6 +271,7 @@ describe('Spies', function() {
         reject: jasmine.createSpy()
       };
       customPromise.resolve.and.returnValue('resolved');
+      spyOn(env, 'deprecated');
       env.configure({ Promise: customPromise });
 
       var spy = env.createSpy('foo').and.resolveTo(42);