Shorten code in rss_get_channel_data()
Coding style
Add atomic option for FileSystemRepository
Crawler append a <link rel="self"> to the feed when it's absent
subscribe method returns Subscription obj
Shorten more code
Merge pull request #27 from Kroisse/polish-rss2

Polish libearth.parser.rss2
Dirty buffer repository
Log when an unknown tag has been found
Add mock into testing dependency
Add test of logging unknown tags
Merge pull request #28 from Kroisse/test_log

Logging
Efficient way to parse revision
Universal context identifier

Copied from SQLAlchemy-ImageAttach
Yay, transactions!
Merge commit ‘master’ and ‘bugs’
Merge branch 'bugs'