Add Gemfile so we use the same jekyll version

Change layout: nil to layout: null so it works again
Add avsnitt.json and JsonHelper which it needs

Credits to http://mathayward.com/jekyll-search/
Add search field and filtering on /arkiv.html

On other pages, press enter to go to /arkiv
While on arkiv, search instantly just by typing

![img](http://cl.ly/image/2S0M451O402S/webbradion-arkiv-search.gif)
Use github-pages gem instead

Github provides this so we can use the exact same gems that they use
Remove JsonHelper and fix avsnitt.json

That plugin would not have worked on github, we would have had to
compile locally on our own.
Use a proper date_to_xmlschema filter so we get a date that angular can
understand.
Remove unused code in avsnitt.json
Add replace filter to remove " that would brake json
Use strip_newlines filter for content, otherwise json is broken
Merge pull request #43 from standout/arkiv-search

Arkiv search