Added opportunity to register mocks.

Allows to register OCMock for specified class in unit tests:
```
- (void)setUp
{
    [super setUp];
    
    self.module = [JSObjectionModule new];
    self.injector = [[JSTestObjectionInjector alloc] initWithContext:@{} andModule:self.module];
    [JSObjection setDefaultInjector:self.injector];
    
    self.testObject = [[JSObjection defaultInjector] getObject:ObjectToTest.class];
}
- (void)test_MyClass_foo_method_is_invoked
{
    id myClassMock = [OCMockObject mockForClass:[MyClass class]];
    [[myClassMock expect] foo];
    [self.injector registerMock:myClassMock forClassOrProtocol:[MyClass class]];
    
    [self.testObject doSomeLogic];
    
    [myClassMock verify];
}
```