Drop support for older versions of D and make safe (#30)

Mostly reverts commit 2339eea

src/room.d

@@ -32,7 +32,6 @@ class Room
 		return room_list[roomname];
 	}
 
-	@trusted  // .values doesn't work with @safe in old D versions
 	static Room[] rooms()
 	{
 		return room_list.values;
@@ -57,7 +56,6 @@ class Room
 			global_room_user_list.remove(username);
 	}
 
-	@trusted  // .keys doesn't work with @safe in old D versions
 	static string[] global_room_users()
 	{
 		return global_room_user_list.keys;
@@ -130,13 +128,11 @@ class Room
 		return user_list.length;
 	}
 
-	@trusted  // .values doesn't work with @safe in old D versions
 	User[] users()
 	{
 		return user_list.values;
 	}
 
-	@trusted  // .keys doesn't work with @safe in old D versions
 	private string[] user_names()
 	{
 		return user_list.keys;

src/server.d

@@ -274,7 +274,6 @@ class Server
 		return null;
 	}
 
-	@trusted  // .keys doesn't work with @safe in old D versions
 	User[] users()
 	{
 		return user_list.values;

src/soulsetup.d

@@ -269,20 +269,12 @@ class Menu
 		actions[index] = action;
 	}
 
-	@trusted  // .keys doesn't work with @safe in old D versions
-	string[] sorted_entry_indexes()
-	{
-		auto indexes = entries.keys;
-		sort(indexes);
-		return indexes;
-	}
-
 	void show()
 	{
 		writefln("\n%s\n", title);
 		if (info.length > 0) writefln("%s\n", info);
 
-		foreach (index ; sorted_entry_indexes)
+		foreach (index ; sort(entries.keys))
 			writefln("%s. %s", index, entries[index]);
 
 		write("\nYour choice : ");