Enable wdm and point to help.jabref.org repo for explanations

Gemfile

@@ -1,2 +1,3 @@
 source 'https://rubygems.org'
-gem 'github-pages'
+gem 'github-pages'
+gem 'wdm', '>= 0.1.0' if Gem.win_platform?

README.md

@@ -1,9 +1,4 @@
-This repository contains the source of the [JabCon homepage](http://jabcon.jabref.org/).
+This repository contains the source of the [JabCon homepage](https://jabcon.jabref.org/).
 Feel free to improve the page or ask a public questions using the [issue tracker](https://github.com/JabRef/JabCon/issues).
 
-Execute `gem install bundler`, `bundle install`, and `bundle exec jekyll serve --baseurl ''` to serve this page locally at http://localhost:4000/.
-Source: https://help.github.com/articles/using-jekyll-with-pages/#installing-jekyll
-Note that browsing the pages does not work locally before Jekyll 3.0, because [Jekyll 2.x cannot deal with URLs indirectly pointing to .html](https://github.com/jekyll/jekyll/pull/3452).
-
-At windows, serving with Jekyll works with [RubyInstaller](http://rubyinstaller.org/downloads) and the [Development Kit](https://github.com/oneclick/rubyinstaller/wiki/Development-Kit).
-[JRuby](http://jruby.org/) doesn't work as the [C extensions were dropped](http://stackoverflow.com/a/32135381/873282).
+For serving the page locally, please see https://github.com/JabRef/help.jabref.org/blob/gh-pages/README.md#installation-of-jekyll-to-check-the-page-locally.