Get Template Part From plugin directory

custom-template-plugin.php

<?php
/**
 * The below function will help to load template file from plugin directory of wordpress
 *  Extracted from : http://wordpress.stackexchange.com/questions/94343/get-template-part-from-plugin
 */ 
 
 define('PLUGIN_DIR_PATH','Your-plugin-directory-path');
 function ccm_get_template_part($slug, $name = null) {

  do_action("ccm_get_template_part_{$slug}", $slug, $name);

  $templates = array();
  if (isset($name))
      $templates[] = "{$slug}-{$name}.php";

  $templates[] = "{$slug}.php";

  ccm_get_template_path($templates, true, false);
}

/* Extend locate_template from WP Core 
* Define a location of your plugin file dir to a constant in this case = PLUGIN_DIR_PATH 
* Note: PLUGIN_DIR_PATH - can be any folder/subdirectory within your plugin files 
*/ 

function ccm_get_template_path($template_names, $load = false, $require_once = true ) {
    $located = ''; 
    foreach ( (array) $template_names as $template_name ) { 
      if ( !$template_name ) 
        continue; 

      /* search file within the PLUGIN_DIR_PATH only */ 
      if ( file_exists(PLUGIN_DIR_PATH . $template_name)) { 
        $located = PLUGIN_DIR_PATH . $template_name; 
        break; 
      } 
    }

    if ( $load && '' != $located )
        load_template( $located, $require_once );

    return $located;
}

index.php

<?php

/**
 * you can call in any wordpress pages or post or else 
 */
 
 ccm_get_template_part('content','custom-page');
 
 // or in  directory
 ccm_get_template_part('folder/content','custom-page');