Update installation.md

Typo error
Create dirs for sockets and pids (otherwise GitLab CI service fails to start correctly)
Merge pull request #234 from WnP/patch-1

Update installation.md
Merge pull request #202 from jtreml/patch-3

Create dirs for sockets and pids (otherwise GitLab CI service fails to s...
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Create dirs for sockets and pids (otherwise GitLab CI service fails to start correctly)
  Update installation.md