embed_item function does not raise if image file not found

Fixes #968
Fix oldstyle object initializer for py26
convert: Test skip existing files

Reproduces #970
convert: Check the correct path when determening whether to skip

Fixes regression from 3197795faaaed07dbd59dc8df41bec791622d759
and makes tests from 56aba87fdc1939bd013fd3e0ba256fafaabfa431 pass.

Fixes #970
Remove unnecessary method on ImportTask
Update type of last_played to library.DateType().
Merge pull request #971 from zacharydenton/patch-1

Update type of last_played to library.DateType().
Changelog for #971
release.py: Fix bumping setup.py version
release.py: Prettify `foo-cmd` in ReST changelog