Updated installation instructions

Split the installation instructions into different sections. Added a section to
explain how to do installation just for the project using Bundler.

Also added instructions how to run jekyll if Bundler has been used to install
the gems.
Track Gemfile.lock.
Updated location
Delete Bremen
Update Events
heilbronn: october event
heilbronn: new member
heilbronn: buga project
Add new blogpost
fix typos
change title
OK Lab München Ort für September Event
Merge pull request #193 from bastiRe/patch-2

OK Lab München Ort für September Event
Homepage link durch pad ersetzt
Merge branch 'gh-pages' of github.com:ironjan/codefor.de into gh-pages
meetings aktualisiert
Update events.yml
Aktualisierung der Code for München Projektseiten
Upadate events
Update meetuplink