doc: jenkins-iojs.nodesource.com -> ci.nodejs.org, iojs.org/download -> nodejs.org/download
The Jenkins URL has changed from https://jenkins-iojs.nodesource.com to https://ci.nodejs.org. The former address now redirects to the latter.
The new download location is https://nodejs.org/download/release/; the configure script was still referring to https://iojs.org/download/release/.
(there are separate commits for these changes)