Configuration: document the node.name option

See https://github.com/elasticsearch/elasticsearch/pull/1345 for the
rationale of visibly documenting this.
Corrected spelling of 'existence' in missing filter
add 0.19.8 download
0.19.8 blog post
Added release notes for 0.19.8 and fixed a typo in the 0.19.8 blog
Guide: Date Histogram Facet examples fix
In the video layout, only render the twitter link if the author has a nick
Added Berlin Buzzwords 2012 videos
Add 'validate' documentation to the API guide
Merge pull request #202 from Simek/patch-1

Guide: Date Histogram Facet examples fix
fixed a typo
Add link to ZooKeeper Discovery Plugin
Merge pull request #205 from imotov/zookeeper-discovery

Add link to ZooKeeper Discovery Plugin
doc the multi index syntax API
mention version
Added link to PlainElastic.Net client
Merge pull request #206 from Yegoroff/patch-1

Added link to PlainElastic.Net client
Cleaned up the copy on Tire on the "Clients & Integrations" page
Added the Chef + EC2 + Vagrant cookbook on the "Clients & Integrations" page

<http://github.com/karmi/cookbook-elasticsearch>
Fixed the `https://` link for Tire on the "Clients & Integrations" page