Fixed uninstall plus WordPress Coding Standards

Hi guelfoweb,
I just fixed a bug in the uninstall [1] and edited all the files so that now they are OK according the WPCS [2].

Please, check these edits before publishing the plugin on the repo. :)

Bye!

[1] delete_option() requires a string, not an array.
[2] http://make.wordpress.org/core/handbook/coding-standards/php/