Code improvements

* Added Plugin URI
* Change link to official Flowplayer plugin
* Correct text domain
* Add inline documentation
* Change code to WordPress coding standards
* Replace global with function for current user
* Have differnt link for when FLowplayer plugin is installed or just not
activated.
* Change the text domain to the current plugin
* Validate data in setting before saving
Merge pull request #2 from grappler/improvements

You sir, are awesome!