2015-07-28 io.js v2.5.0 Release

Notable changes

* **https**: TLS sessions in Agent are reused (Fedor Indutny)
https://github.com/nodejs/io.js/pull/2228.
* **src**: base64 decoding is now 50% faster (Ben Noordhuis)
https://github.com/nodejs/io.js/pull/2193.
* **npm**: Upgraded to v2.13.2, release notes can be found in
<https://github.com/npm/npm/releases/tag/v2.13.2> (Kat Marchán)
https://github.com/nodejs/io.js/pull/2241.

PR-URL: https://github.com/nodejs/io.js/issues/2239