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.
Aktualisierung der Code for München Projektseiten
added event: occ14
Merge pull request #198 from marcel12bell/gh-pages

new date oklab cologne
Merge pull request #197 from stkdiretto/gh-pages

added event: occ14
update events
update events

Conflicts:
	_data/events.yml
new blogpost jugend hackt
add new photo for jugendhackt
add chemnitz event
Added Stuttgart Sep 2014 Meet-Up
update events
Updated OK Lab Leipzig event
Merge pull request #199 from CodeforLeipzig/update-events

Updated OK Lab Leipzig event
Update events.yml
Update index.html
Merge pull request #189 from johnjohndoe/feature/add-gemfile-lock

Track Gemfile.lock.
Merge pull request #88 from CodeforLeipzig/update-installation-instructions

Updated installation instructions
Merge pull request #195 from konstin/gh-pages

Aktualisierung der Code for München Projektseiten