getTumblelogs can get form_key and channel_id
Introduce sendInfo in getCachedTumblrInfo method
Get multi tumblelogs when Tumblr request fails
post should throw error when it can't find channel_id in blogs
Refine Tumblr Extractor
Throw error in Models.getMultiTumblelogs
Merge pull request #157 from syoichi/pr21-tumblr

Improve Tumblr Model, Extractor, Models.getMultiTumblelogs