Added ListEventsRecievedByUser

Added functionality for ListEventsRecievedByUser. Api reference: http://developer.github.com/v3/activity/events/#list-events-that-a-user-has-received
add Arıl Bozoluk to AUTHORS and CONTRIBUTORS
remove unnecessary type declarations

when initializing a slice of concrete structs, it's not necessary to
declare the type of each item in the slice, since the compiler knows
what you mean.
move package docs to doc.go

our package docs are too long yet to really need to be in their own
file, but I'd like to flesh them out a bit more, particularly once #19
is resolved.
ok