expand readme

increase version commit to match git tag

Add date filter (#36)

* add docs for end date

* refactor transformers

* add start and end transformers, but broke them all

* uhhh this isnt working...

* ok seems to work now

* modify to require rfc339

Bump version to v2.2.0 with polarstep import option

bump version with compression

update version with new arguments

bump version to v1.2.0

bump version to v1.1.0

improved error messages

upgrade dependencies