Update README.md

Clarifies and adds to description of the use of formsets.
Update README.md
Merge branch 'master' of https://github.com/kurtw/cms-toolkit
Add remove button functionality to the formset
Remove support for date
Merge branch 'master' of https://github.com/kurtw/cms-toolkit
Merge pull request #22 from kurtw/master

Update README and add formset remove button