Issue #310

http://code.google.com/p/jsplumb/issues/detail?id=310

First commit makes sure that the endpoint's cssClass option is applied to its copies created during creation of a connection.

3rd commit makes sure that the cssClass option is applied to endpoints.

4th commit adds a new global property: floatingEndpointClass. A CSS class name that is applied to floating endpoints. By adding `visibility: hidden` to _jsPlumb_endpoint_floating class, the floating endpoint does not peek from underneath the real endpoint and hopefully everything still works ;)

![No floating endpoint class](https://f.cloud.github.com/assets/301053/65883/0a69695a-5e90-11e2-89dc-9a362eb645a1.png)
![With floating endpoint class](https://f.cloud.github.com/assets/301053/65884/10abfbb6-5e90-11e2-8621-4251a307f8f8.png)