readme: Update badges

Travis no longer needs the "secure" subdomain for HTTPS.

Both Travis and Version Badge support SVG for HiDPI displays.
syntax
Update README.md

Added documentation to use redis adapter to a redis instance that has a password.
Merge pull request #24 from Siedrix/patch-1

Update README.md
Merge pull request #12 from Krinkle/patch-1

readme: Update badges
Fixed merge conflicts on Socket.io 1.1.0 update