v3.0.1

Migrate to Null-Safety (#91)

* refactor(nnbd): migrate to null-safety

* refactor(deps): remove merge_map package

* refactor(deps): remove color package

* chore(format): fix format

* feat(cli): support option of --no-sound-null-safety

* refactor(integration): add name of params

* refactor(nndb): add option for pubspec.yaml

* refactor(cli): remove unused var

* refactor(*): copy from dart_style

* refactor(*): refactor

* refactor(plugin): remove color libs

* refactor(plugin): remove color libs

* chore(deps): update deps

* chore(deps): update deps

* chore(analyze): fix analyze points

* chore(deps): add collection

* docs(changelog): update

* chore(*): update deps

* chore(*): bump up 3.0.1

* chore(*): bump up 3.0.1

* chore(deps): update deps

* chore(deps): update deps in sample