Change refs for joyent/libuv repo to libuv/libuv

* References to old repository found through grepping
* Replace references from github.com/joyent/libuv to github.com/libuv/libuv
* Fix previous commit by not including whitespace changes

 For issue #1560.
Merge pull request #1562 from Happy-Dude/fix-1560-libuv-refs

Change refs for joyent/libuv repo to libuv/libuv.