Add version display while starting Nadeko

This will help to troubleshoot errors if someone hasn't the last version of Nadeko

src/NadekoBot/NadekoBot.cs

@@ -12,6 +12,7 @@ using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using System.Threading.Tasks;
+using NLog.Fluent;
 
 namespace NadekoBot
 {
@@ -31,6 +32,9 @@ namespace NadekoBot
         public async Task RunAsync(string[] args)
         {
             SetupLogger();
+            _log = LogManager.GetCurrentClassLogger();
+
+            _log.Info("Starting NadekoBot v" + typeof(NadekoBot).GetTypeInfo().Assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>().InformationalVersion);
 
             //create client
             Client = new DiscordSocketClient(new DiscordSocketConfig
@@ -47,7 +51,6 @@ namespace NadekoBot
             Google = new GoogleApiService();
             CommandHandler = new CommandHandler(Client, Commands);
             Stats = new StatsService(Client, CommandHandler);
-            _log = LogManager.GetCurrentClassLogger();
 
             //init db
             using (var context = DbHandler.Instance.GetDbContext())

src/NadekoBot/Properties/AssemblyInfo.cs

@@ -8,6 +8,7 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct("NadekoBot")]
 [assembly: AssemblyTrademark("")]
+[assembly: AssemblyInformationalVersion("1.0-alpha")]
 
 // Setting ComVisible to false makes the types in this assembly not visible
 // to COM components.  If you need to access a type in this assembly from