* Lint error corrected
* test improved
* lint error corrected in test file
* readme corrected
* test improved
* test of document page history workflow added
* CI error corrected
* dreipst comment
* Migration to new api improved in model's file and data tag remove in xml file
* code totally migrate to odoo 9.0 api
* test bug fixed
* test error fixed
* Lint error improved
[IMP] - Improved views to match document_page improvements.
[IMP] - Added notification to followers when a new version is approved.
[ADD] - Updated document_page_approval pot and added es translations.
[IMP] - document_page_approval: Updated spanish translation.