Improving error message when installing a plugin on the wrong LS version

Imagine you have LS version `2.0.0` and you're trying to install a version of a plugin that is only able to work on previous versions ( in this example < `2.0.0` ), the error you're getting now is something like:

```
purbon-elastic% bin/plugin install logstash-input-file
Validating logstash-input-file
Installing logstash-input-file
Plugin version conflict, aborting
ERROR: Installation Aborted, message: Bundler could not find compatible versions for gem "logstash-core":
In snapshot (Gemfile.lock):
logstash-core (= 2.0.0)

In Gemfile:
logstash-input-file (>= 0) java depends on
logstash-core (< 2.0.0, >= 1.4.0) java

logstash-core (= 2.0.0) java

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.
Bundler could not find compatible versions for gem "logstash":
In Gemfile:
logstash-input-file (>= 0) java depends on
logstash (< 2.0.0, >= 1.4.0) java
Could not find gem 'logstash (< 2.0.0, >= 1.4.0) java', which is required by gem 'logstash-input-file (>= 0) java', in any of the sources.
```

this error should be catchup and improved to provide a simple message to the end user.