Add setPlayerGroup in API

src/net/crystalyx/bukkit/simplyperms/SimplyAPI.java

@@ -31,6 +31,12 @@ public class SimplyAPI implements PermsConfig {
 		refreshPermissions();
 	}
 
+	@Override
+	public void setPlayerGroup(String player, String group) {
+		plugin.config.setPlayerGroup(player, group);
+		refreshPermissions();
+	}
+
 	@Override
 	public void addPlayerGroup(String player, String group) {
 		plugin.config.addPlayerGroup(player, group);

src/net/crystalyx/bukkit/simplyperms/io/ConfigFile.java

@@ -36,6 +36,12 @@ public class ConfigFile implements PermsConfig {
 		plugin.getConfig().set("users/" + player + "/groups", (groups.isEmpty()) ? null : groups);
 	}
 
+	@Override
+	public void setPlayerGroup(String player, String group) {
+		removePlayerGroups(player);
+		addPlayerGroup(player, group);
+	}
+
 	@Override
 	public void addPlayerGroup(String player, String group) {
 		player = player.toLowerCase();

src/net/crystalyx/bukkit/simplyperms/io/ConfigSQL.java

@@ -113,6 +113,12 @@ public class ConfigSQL implements PermsConfig {
 		}
 	}
 
+	@Override
+	public void setPlayerGroup(String player, String group) {
+		removePlayerGroups(player);
+		addPlayerGroup(player, group);
+	}
+
 	private void addPlayerGroup(String player, String group, boolean first) {
 		if (init()) {
 			try {

src/net/crystalyx/bukkit/simplyperms/io/PermsConfig.java

@@ -11,6 +11,8 @@ public interface PermsConfig {
 
 	public void removePlayerGroup(String player, String group);
 
+	public void setPlayerGroup(String player, String group);
+
 	public void addPlayerGroup(String player, String group);
 
 	public void addPlayerPermission(String player, String permission, boolean value);