Add expiration block and date to profiles

[vsund]

Would be handy to have a small notice of expiry in the profile view (and if an ID is really close, maybe even a notice modal on other views). Might be even more useful if you place some instructions for renewal there.

Needs: https://github.com/blockstack/blockstack-core/issues/353 Also related: https://github.com/blockstack/blockstack-explorer/issues/29

[larrysalibra]

Great suggestion.

[moxiegirl]

@markmhx @jeffdomke Can we bump this up? It takes people by surprise. I'll link my related issue.

[markmhendrickson]

@moxiegirl I plan to triage the issues on this repo's board soon and will see about getting this one prioritized in light of other ones I surface 👍🏻

[friedger]

fixed by #1924