model rollback functionality
corrected a syntax error and changed the doc text
advanced rollback functionality and  multiple models handling
corrected rollback's doc in model
make the function operate on dirty non new models
robust and simplified tests that checks against values
Merge branch 'master' of https://github.com/GroupTalent/epf

# By Stephen McGinty (2) and Taras Mankovski (1)
# Via Gordon L. Hempton (2) and Taras Mankovski (1)
* 'master' of https://github.com/GroupTalent/epf:
  Clarified the meaning of update
  Modified previous patch to match the comment on it
  Models with missing embedded keys can now be loaded
remove model from originals on rollback
load lazy models only when they have a session
Merge branch 'fix-lazy-models' of https://github.com/belluzj/epf
Merge branch 'master' of https://github.com/g13013/epf