Announce new features

[efc]

It would be nice if SubCalc would let users know about upgrades and new features. I imagine this could work by saving the last version used in the subcalc3 local storage and creating a list of features per version. Then if the last version used differed from the current version, the app could show a friendly card with information about each update in between the two to bring users up-to-speed.

Of course, if someone uses SubCalc on more than one device or in more than one browser, seeing these notices over and over could become tedious. So maybe something less intrusive would be better? Maybe just a growl notice with a link to tap for more details?

Anyway, saving the "last version used" would be a good place to start.