Update express-session to version 1.15.3 🚀

[greenkeeperio-bot]

🚨🔥⚠️ Action required: Switch to the new Greenkeeper now! 🚨🔥⚠️
This version of Greenkeper will be shutdown on May 31st.
With Integrations first-class bot support landed on GitHub and we’ve rewritten Greenkeeper to take full advantage of it. Simpler setup, fewer pull-requests, faster than ever.

---

Hello lovely humans,

express-session just published its new version 1.15.3.

State	Update 🚀
Dependency	express-session
New version	1.15.3
Type	dependency

This version is not covered by your current version range.

Without accepting this pull request your project will work just like it did before. There might be a bunch of new features, fixes and perf improvements that the maintainers worked on for you though.

I recommend you look into these changes and try to get onto the latest version of express-session.
Given that you have a decent test suite, a passing build is a strong indicator that you can take advantage of these changes by merging the proposed change into your project. Otherwise this branch is a great starting point for you to work on the update.

Do you have any ideas how I could improve these pull requests? Did I report anything you think isn’t right?
Are you unsure about how things are supposed to work?

There is a collection of frequently asked questions and while I’m just a bot, there is a group of people who are happy to teach me new things. Let them know.

Good luck with your project ✨

You rock!

🌴

---

GitHub Release

• deps: debug@2.6.7
  • deps: ms@2.0.0

---

The new version differs by 69 commits .

• ff4c511 1.15.3
• 0595f89 build: Node.js@7.10
• 4866502 build: express@4.15.3
• 98b9005 deps: debug@2.6.7
• 762c041 docs: add express-session-cache-manager to the list of session stores
• d0df7ab docs: add note that req.session.id is alias of req.sessionID
• e01ca86 docs: add connect-memjs to the list of session stores
• 32c2b10 build: Node.js@7.9
• 4aa57a0 deps: debug@2.6.6
• d051890 1.15.2
• 4b033b3 docs: fix rendering of express-sessions store in list
• b5a0437 deps: debug@2.6.3
• 5fd74d2 build: fix istanbul ignore scope
• 3a7e3d2 deps: debug@2.6.2
• 4a4c2ef tests: remove express from more tests

There are 69 commits in total. See the full diff.

---

This change is