docs: include mention of new crypto methods

Include mention of privateEncrypt and publicDecrypt in changelog.

PR-URL: https://github.com/iojs/io.js/pull/722
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>

CHANGELOG.md

@@ -7,6 +7,7 @@
 * debug: fix v8 post-mortem debugging.
 * crypto: publicEncrypt now supports password-protected private keys.
 * crypto: ~30% speedup on hashing functions.
+* crypto: added privateEncrypt/publicDecrypt functions.
 * errors
   - better formatting via util.inspect
   - more descriptive errors from fs. This necessitated a `NODE_MODULE_VERSION` bump.