Outdated recognition dates for sponsors

[kacollins]

These links show that sponsors will be recognized at meetups "from May 2016 - April 2017":
https://donate.techlahoma.org/sponsorship
https://donate.techlahoma.org/donations/new?plan_id=bootstrap-funder
https://donate.techlahoma.org/donations/new?plan_id=angel-investor

[kacollins]

These dates were updated at one point, but are still very outdated (currently "from May 2017 - April 2018"). How about changing it to something more like "within 12 months of donation"?