remove RbStory.history re-introduced by bohansen_release_chart. Journals are gone
patch ReleaseBurndown to gracefully do nothing if there is no closed sprint
implement sprints and closed_sprints for release as AR relations
rename story.release to story.release_burndown_data
remove snaphot feature
use uppercase for Remaining story points text
release csv export: avoid error if bd is empty
fix output of javascript release burndown.charts for Rails3
avoid error on jqplot init when there is no data