Added ability to clone components

- Added Node::CloneComponent to clone components existing in other
nodes.
- Added log warning to Node::AddComponent if the component already has a
parent node.
Expose CloneComponent() function to AngelScript & Lua and make it return the created component.
Travis CI: API documentation update at 2014-05-04 23:17:49 UTC.
[ci package]
For Travis CI - switch CI build to use OS X build environment.