check local date time vs server date time for prereg stations
this raises an alarm to the user on the registration checkin page to catch the following (STUPID) scenario:
  browser system clock is wrong, and SSL certs from Stripe are invalid because they're in the future (because, let's say, your crappy laptop has no battery and thinks it's Jan 1st 1970)
   this was an actual bug we encountered.  crazy.

this is WIP but probably ready to go
Update configspec.ini

fix typo
Merge pull request #551 from magfest/server_browser_date_time_mismatch_check

check local date time vs server date time for prereg stations