lock compile directory

app/coffee/Errors.coffee

@@ -12,6 +12,14 @@ FilesOutOfSyncError = (message) ->
 	return error
 FilesOutOfSyncError.prototype.__proto__ = Error.prototype
 
+AlreadyCompilingError = (message) ->
+	error = new Error(message)
+	error.name = "AlreadyCompilingError"
+	error.__proto__ = AlreadyCompilingError.prototype
+	return error
+AlreadyCompilingError.prototype.__proto__ = Error.prototype
+
 module.exports = Errors =
 	NotFoundError: NotFoundError
 	FilesOutOfSyncError: FilesOutOfSyncError
+	AlreadyCompilingError: AlreadyCompilingError