Merge pull request #74 from kl/master

Check if valid Youtube extension
Added 'MIT' as the license to the gem
Restore 1.8.7 compatibility by pinning down mime-types gem version.
Merge pull request #80 from kl/master

Fixed some failing specs and added the aria2 downloader
Fiddle around with dependencies a bit more.
Fix missing dependency line
Add wget user agent to aria downloader. This fixes the arte plugin which will redirect to rtmp:// otherwise.
Make aria use wget user header
Bump version
fix proper format selection given only extension

if video formats are not seeded through available formats, resulting url is sometimes nil even while valid format existed

  For instance: ViddlRb::Youtube.get_urls_and_filenames("http://www.youtube.com/watch?v=WawU4ouldxU",{:quality => {:extension => "mp4"}})
  (video has valid format 22, but returns nil because it finds non-existent 38 first)
update youtube formats list

according to http://stackoverflow.com/questions/18876872/how-to-get-the-lowest-quality-youtube-video
add some formats from wikipedia
returned default format order array for 1.8.7
Setting mechanize gem version to keep Ruby 1.8.7 compatibility
Merge pull request #82 from ggarnier/master

Setting mechanize gem version to keep Ruby 1.8.7 compatibility
Merge pull request #81 from snusmu/master

youtube plugin update