Update doc/articles/handling-private-packages-with-satis.md

Added the stability flag to this article, was a little confusing as to why satis didn't install correctly using this article. Turned out the github composer/satis README had the answer so i've put it here also.

Matt
added hg support for Package\Locker
replicate the git behvaiour to resolve a feature's version for mercurial
Fixed phpdoc
Merge pull request #1518 from deguif/master

Fixed phpdoc in JsonFile::read()
Merge pull request #1512 from mattkirwan/patch-1

Added stability flag to the install code: doc/articles/handling-private-packages-with-satis.md
Merge remote-tracking branch 'xrstf/mercurial-support'
Add php-64bit package if the php version has 64bit ints, fixes #1506, fixes #1511
Add 64bit package to docs