Add support for Spring 3

[pvorb]

atmosphere-spring brings support for Spring 4.

With the current code, it is almost impossible to integrate atmosphere-spring into a Spring 3 project due to a missing method in BeanFactory (i.e. ApplicationContext) which was added in Spring 4.1: <T> T getBean(Class<T> requiredType, Object... args) throws BeansException;

This PR replaces the use of T getBean(Class<T> requiredType, Object... args) by Object getBean(String name, Object... args), which has been around since Spring 2.5. This way, you can also use atmosphere-spring with older Spring versions.

Changing the property spring-version to 3.2.x is not mandatory but might help to assert future changes won't break compatibility with Spring 3.

[pvorb]

This change should fix issue #187.

[jfarcand]

@pvorb It would be better if both version are supported. Should be easy to rework your patch to use reflection and detect the version used. So just update and I will merge and release

[pvorb]

@jfarcand With my fix, both Spring 3 and Spring 4+ are supported, since the old method is supported in newer versions. It is not marked as deprecated, so it will stay for a few versions of Spring.