Exported timer class.
updated .gitignore to not ignore index.js
Added an "add-on" flag (un-used for the moment)
removed initItems and deinitItems from sequence using container methods instead.
Added support for "document".
Fix so that the constructor of a derived model is called correctly.
Several improvements related to history api changes.
Added a historyApi using function to enable/disable history api.
released sequences so that destruction is also tested.
Bumped to version 0.2.8