Make chruby plugins conform to naming convention

diff --git a/plugins/available/chruby-auto.bash b/plugins/available/chruby-auto.plugin.bash
similarity index 100%
rename from plugins/available/chruby-auto.bash
rename to plugins/available/chruby-auto.plugin.bash

diff --git a/plugins/available/chruby.bash b/plugins/available/chruby.plugin.bash
similarity index 100%
rename from plugins/available/chruby.bash
rename to plugins/available/chruby.plugin.bash