Prepare release: Bump version to 0.2.8

Config.xcconfig

@@ -1,5 +1,5 @@
 APP_DISPLAY_NAME = Trio
-APP_VERSION = 0.2.7
+APP_VERSION = 0.2.8
 APP_BUILD_NUMBER = 1
 COPYRIGHT_NOTICE =
 DEVELOPER_TEAM = ##TEAM_ID##