App-Server support mapping

[damontecres]

I am thinking of tying each future minor release of this app to a minimum version of the server. This would start with app version 0.3.0.

So something like this:

App	Minimum Server
0.3.x	0.25.x+
0.4.x	0.26.x+
0.5.x	0.27.x+

The server does a great job at deprecating features for a few releases, so it is tough to define a maximum supported server version for the app.

#309 raises the minimum version for 0.3.0.

Legacy: The app versions before 0.3.0 (ie 0.0.x, 0.1.x, & 0.2.x) required a server of at least 0.23.0, but this wasn't thoroughly tested, so your mileage may vary.