This repository and its contents are specific to the 1.4 branch of Logstash. Beginning with Logstash 1.5, a new plugin management system was put into place. No longer will all plugins be shipped with the Logstash core, they will be completely independent from one another.
This means that new pull requests will not be accepted here. This also means that any existing pull requests will likely need to be rerouted to their new repository. You can find where the new plugin repository is below.
Repositories are now in github.com/logstash-plugins and have a logstash-{type}-{name} syntax, where type is one of input, codec, filter, or output. For example, the Elasticsearch output plugin is at github.com/logstash-plugins/logstash-output-elasticsearch, and the collectd codec is at github.com/logstash-plugins/logstash-codec-collectd.