Add paging support for Github requests

[gregturn]

No description provided.

[gregturn]

@bclozel I rebased this PR against latest master.

Also, I tried to configure Eclipse Code Formatter, but it still won't apply imports in the proper order.

[bclozel]

This won't work since we're already using that key to cache objects of types T. So fetching from the cache using an URL, you can get the wrong thing depending on the method.

Also, ResponseEntity is not serializable and that won't work with the default JDK serializer used by the redis cache manager. See CacheConfig for the configuration used for other types.

[bclozel]

I should review the current caching infrastructure because this is not making it easier to leverage more caching.
Note that I can't merge this right now as this throws the following as soon as we're trying to cache data:

ERROR 14 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet] : 
Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed;
nested exception is org.springframework.data.redis.serializer.SerializationException: Cannot serialize; 
nested exception is org.springframework.core.serializer.support.SerializationFailedException: Failed to serialize object using DefaultSerializer;
nested exception is java.lang.IllegalArgumentException: DefaultSerializer requires a Serializable payload but received an object of type [org.springframework.http.ResponseEntity]] with root cause

[gregturn]

Digging further in, I actually need the ResponseEntity version of this RestTemplate's response because I need access to the content as well as the headers (the Link header to be precise). Given all that, it would appear that flagging this as cacheable isn't the right solution. I'll amend the PR.

[gregturn]

@bclozel Friendly ping.

[bclozel]

This part has been moved to sagan-renderer and supports now paging for requests to GitHub.
Thanks!