PSR-0 Composer Autoloading causing class not found in plugin
Problem was with how composer handles psr-0 and psr-4 autoloading, so by changing the composer.json like such, the classes were loaded.

{
  "autoload":{
    "psr-4": {"PluginX\\": "PluginX/"}
  },
  "require": {
    "andrefelipe/orchestrate-php": "0.14.0"
  }
}