Migrate to com.github.spring-social organization

[mlaccetti]

Hi @sachin-handiekar - I am the maintainer of spring-social-google, and recently had to rename our package for release from org.springframework.spring-social:spring-social-google to com.github.spring-social for Maven Central sync reasons. As such, we created the spring-social organization on GitHub. Since you maintain a project, I was wondering if you wanted to move it under the same organziation, to help bring active projects together, engage the community, etc.