add initial support for Vkontakte and Vk.com embedded frames
use decode_entities(), add versioning of the plugin, proper file suffix

during Nigel Taylor's review he proposed several patches
- use more advanced decode_entities() instead of s/// for one case
- add versioning to module (with this changed jumped to 0.02)
- set file suffix according to content
lowering version again as 0.01 didn't reach main repository anyway
fixing string comparison
decode HTML entities in URL if iframe needs it
remove decoding HTML entities from Vk.com code, simplify the code
remove unused `use HTML::Entities'
Merge pull request #111 from sleep-walker/master

add support for vkontakte.ru (and vk.com)