server-app: make _sortLayersByPhase stable

Fix the phase-sorting algorithm to use a stable sorting algorithm,
since the built-in `Array.prototype.sort` is not stable.
Merge pull request #925 from strongloop/fix/stable-sort-for-middleware

server-app: make _sortLayersByPhase stable
v2.8.6
Merge branch 'release/2.8.6' into production
Merge tag 'v2.8.6'

2.8.6

 * server-app: make _sortLayersByPhase stable (Miroslav Bajtoš)

 * Rework phased middleware, fix several bugs (Miroslav Bajtoš)
Update README.md

Add mention of slc and Arc to README
Merge pull request #2 from strongloop/master

update