make save button primary, if it's the only button on the page

For example, this happens when used with django-reversion.
fix <th> elements for tabular inline
remove table-striped from tabular inline so it looks less chaotic
add django-reversion and django-reversion-compare Bootstrap templates
Merge pull request #35 from ejnens/master

Django-reversion templates and some minor improvements
Fix to allow use inline forms with non editable custom pk in models
Small cosmetic fix of tabular inline template
Merge pull request #36 from alrusdi/inline-forms

"This changes allows to use inline forms with models containing non editable custom pk" by: @alrusdi