Cannot install plugin on CentOS 7.4.1708

[aworstell]

Hello,
I have CentOS 7.4.1708 and ruby-2.0.0.648-33 and am trying to install the plugin, and getting the following error:
[root@ppas-metrics-1 postgres]# pg_monitor install -l $KEY /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in require': cannot load such file -- bundler/setup (LoadError)
from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in require' from /usr/local/share/gems/gems/newrelic_postgres_plugin-0.3.0/lib/newrelic_postgres_plugin.rb:2:in <top (required)>'
from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in require' from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:55:in require'
from /usr/local/share/gems/gems/newrelic_postgres_plugin-0.3.0/bin/pg_monitor:3:in <top (required)>' from /usr/local/bin/pg_monitor:23:in load'
from /usr/local/bin/pg_monitor:23:in <main>'