Check if installed Mono version is up to date

[pixelomer]

The Celeste script currently only checks for the existence of the mono binary but doesn't check the version. The default repositories generally have very outdated versions of Mono and there has been at least one instance where a user encountered a crash by launching Celeste with an old version of Mono (Debian 4.6.2.7+dfsg-1ubuntu1).

Crash output:

Can't find custom attr constructor image: /home/<user>/Desktop/Celeste/FNA.dll mtoken:0x0a000001 due to Could not load file or assembly or one of its dependencies. assembly:System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 type:<unknown type> member:<none>
Stacktrace:

  at <unknown> <0xffffffff>
  at SDL2.SDL.SDL_RWFromFile (string,string) <0x00017>
  at SDL2.SDL.SDL_GameControllerAddMappingsFromFile (string) <0x0001f>
...