correct action hook for register_admin_styles

Changed the action hook from 'admin_print_styles' to 'admin_enqueue_scripts' which is better.

See: http://codex.wordpress.org/Plugin_API/Action_Reference/admin_enqueue_scripts

See: http://make.wordpress.org/core/2011/12/12/use-wp_enqueue_scripts-not-wp_print_styles-to-enqueue-scripts-and-styles-for-the-frontend/
Removed the need to customize url for wp_enqueue_style and wp_enqueue_scripts

By adding the __FILE__ magic constant as a second parameter to the wp_enqueue_style and wp_enqueue_scripts, the user no longer needs to change 'plugin-name'. This also makes the code more robust.
Added Plugin Settings page (commented out)

Added a Plugin Settings page, that can be enabled by uncommenting the line that hooks it into the admin_menu action hook.

Added additional views that contain the WordPress standard markup to wrap the plugin settings markup.

The views are now loaded into the plugin page.
Restricted scripts and styles to load only on plugin settings page if it is enabled.

If the Settings page has been activated, the scripts and styles will only be loaded on the settings page. If not, they will be loaded for all admin pages (like before this commit)

Also added the __FILE__ magic constant as a second parameter to the admin_enqueue_style and admin_enqueue_script, the user no longer needs to change 'plugin-name'. This also makes the code more robust.
Merge pull request #24 from Japh/master

Suggested fix for #22
Merge pull request #27 from mikkelbreum/master

improvements and additions (added settings page)
implemented the singleton pattern
added access modifiers
removing whitespace between exit and the parens
updating a code comment
removing whitespace at the bottom of the file
combining both the admin_open and admin_close into a single file. localizing the text.
removing the open/close files and combining them into a single admin view
initializing instance to null, initializing the plugin_screen_slug to null,  updating coding conventions, improving comments, updating conditionals,
disable the admin menu by default
improving documentation
updating the read me file for 2.0
removing whitespace at the end of the file
updating some of the grammar
Update README.md