autorefresh the page occasionally

[erosson]

http://www.reddit.com/r/swarmsim/comments/2f54ln/017_better_buy_buttons/ck63zvt

we probably don't want ancient versions of the game running

[erosson]

on second thought, this is more complex than just refreshing - I want people to be able to play offline on their phones, it's okay to let the page go out of date if there's no connection. maybe ping to test for connectivity first.

in fact, we can treat this like any other autoupdater: periodically ask the server what the current version is ($interval $http.get /version.txt), and then

• do nothing if the server doesn't respond
• do nothing if we're up-to-date already
• refresh the page if the server is available and responds that we're out of date

[erosson]

I said reopen

[erosson]

auto-update pings are combined with timecheck pings, so no new traffic added for this.

if we're offline, it'll give up and do nothing.

[Shoelace]

the appcache mechanism in #388 caters for some of this. allowing offline access.. notification of new version etc..