Remember last seen server version number

Given that we are now only checking for new versions
every 2 weeks, remember the last version seen
and use that to report whether or not the current
version is outdated when we're not actually asking
the server.

We're remembering the last seen version using the
new settings system.

If there is no last seen version, or if it's malformed,
we just return version 0.0.0

Author: samaaron

app/server/sonicpi/lib/sonicpi/spider.rb

@@ -94,7 +94,7 @@ def __server_version(url="http://sonic-pi.net/static/info/latest_version.txt")
           (Time.at(last_update) < Time.now)
         two_weeks_in_seconds = 60 * 60 * 24 * 14
         ts_2_weeks_later = Time.at(last_update + two_weeks_in_seconds)
-        return Version.new(0) if Time.now < ts_2_weeks_later
+        return __local_cached_server_version if Time.now < ts_2_weeks_later
       end
 
       begin
@@ -109,9 +109,18 @@ def __server_version(url="http://sonic-pi.net/static/info/latest_version.txt")
         v_string = response.body
         v = Version.init_from_string(v_string)
         @settings.set(:last_update_check_time, Time.now.to_i)
+        @settings.set(:last_seen_server_version, v.to_s)
         v
       rescue
-        Version.new(0)
+        __local_cached_server_version
+      end
+    end
+
+    def __local_cached_server_version
+      begin
+        return Version.init_from_string(@settings.get(:last_seen_server_version))
+      rescue
+        return Version.new(0)
       end
     end