Component removal and HasNot fix

[natebot13]

Description

fixes #9 fixes #12 Merges Bill Haggerty's fork for their component removal fix and my HasNot fix.

As Oxygen is written currently, components are marked for removal but never actually removed, and HasNot filters don't work for components that are added after initialization. This PR fixes both of these two issues. Also bumped the min dart version to allow for constructor tear-offs.

Checklist

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• [x] All existing and new tests are passing.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] The dart analyzer (dart analyze) does not report any problems on my PR.
• [x] I read and followed the Effective Dart Style Guide.
• [x] I have added a description of the change under [next] in CHANGELOG.md.
• [x] I am willing to follow-up on review comments in a timely manner.
• [x] I am happy with the current version of this PR and it is ready to be reviewed

Breaking Change

Does your PR require Oxygen users to manually update their apps to accommodate your change?

• [ ] Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md).
• [x] No, this is not a breaking change.

Related Issues

• #9
• #12

[wolfenrain]

~~@natebot13 just checking in if you are able to follow-up on the above review?~~

Seems I never submitted my review.. my bad

[wolfenrain]

@natebot13 do you have the time to follow-up on this?

[natebot13]

Sure I've got some time this week, if not tonight! Thanks for reviewing!

[natebot13]

Yo, it's been a while. Would love to get this in!