added github_events_agent with changes for RAM conserving gem dependencies

this patch contains a github event client , just provide a username or organisation and keep track of your github events 

i havn't made that for any options to track individual repositories, but that could easily be added.
i will look at that, there are just so many thinks you could do with the github api, i don't know if it will make the agent to complex to use, maybe it is better to break the agent down in different ones like the twitter agent