ソースコード修正時にファイルエンコーディングがBOM付きUTF-8かどうかをチェックする ref: http://qiita.com/snaka/items/ae01990b147570fa0e75

SourceFileEncodingChecker.cs

using UnityEditor;
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.IO;

public class SourceFileEcodingChecker : AssetPostprocessor {
    static Regex m_SourceFilePattern;

    static SourceFileEcodingChecker() {
        m_SourceFilePattern = new Regex(@".+\.cs");
    }

    static void OnPostprocessAllAssets(
        string[] importedAssets,
        string[] deletedAssets,
        string[] movedAssets,
        string[] movedFromAssetPaths) {

        var invalidFiles = new List<string>();

        foreach (var importedAsset in importedAssets) {
            if (m_SourceFilePattern.IsMatch(importedAsset)) {
                var dataPath = Application.dataPath;
                dataPath = dataPath.Substring(0, dataPath.Length - 7);

                var path = System.IO.Path.Combine(dataPath, importedAsset);

                Debug.Log ("*** import: " + path);

                using(FileStream fs = File.OpenRead(path)) {
                    var head = new byte[3];
                    fs.Read (head, 0, 3);
                    var headStr = System.BitConverter.ToString(head);
                    Debug.Log (headStr);
                    if (headStr != "EF-BB-BF") {
                        invalidFiles.Add(path);
                    }
                    fs.Close ();
                }
            }
        }

        if (invalidFiles.Count > 0) {
            EditorUtility.DisplayDialog(
                "File encoding check error", 
                string.Join ("\n",invalidFiles.ToArray ()),
                "OK"
            );
        }
    }
}