Error installing logstash-output-elasticsearch-license plugin

Based on the instructions [here](https://www.elastic.co/guide/en/watcher/current/logstash-integration.html), I'm getting the following error when trying to install the logstash license plugin. I'm using logstash 1.5.4, installed using yum on CentOS 6.7.

```
$ sudo /opt/logstash/bin/plugin install logstash-output-elasticsearch-license
Validating logstash-output-elasticsearch-license
Installing logstash-output-elasticsearch-license
Plugin version conflict, aborting
ERROR: Installation Aborted, message: Bundler could not find compatible versions for gem "logstash-output-elasticsearch":
In snapshot (Gemfile.lock):
logstash-output-elasticsearch (= 1.0.7)

In Gemfile:
logstash-output-elasticsearch_http (>= 0) java depends on
logstash-output-elasticsearch (>= 0) java

logstash-output-elasticsearch-license (>= 0) java depends on
logstash-output-elasticsearch (~> 0.2) java

logstash-output-elasticsearch_http (>= 0) java depends on
logstash-output-elasticsearch (>= 0) java

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.
```

Start by reproducing the installation command on the stated Logstash 1.5.4 CentOS environment, then inspect the Gemfile.lock entries for logstash-output-elasticsearch and the license plugin requirements shown in the error. Done means the license plugin installs without a dependency conflict, or the incompatibility is clearly documented.

Written by the indexing model from the issue text.