Added logfile support

src/logger.cr

@@ -35,6 +35,7 @@ module Logger
 
   @@min_level : LOG_LEVEL = LOG_LEVELS["INFO"]
   @@max_level : LOG_LEVEL = LOG_LEVELS["FATAL"]
+  @@log_file : String? = nil
   @@debug : Bool = false
 
   LOG_MUTEX = ::Mutex.new
@@ -83,6 +84,9 @@ module Logger
     @@min_level.to_s.downcase
   end
 
+  def self.log_file=(@@log_file : String)
+  end
+
   def self.valid?(level : LOG_LEVEL) : Bool
     level.in?(@@min_level.value..@@max_level.value)
   end
@@ -100,7 +104,13 @@ module Logger
     if valid?(_level) || debug?
       synchronize {
           time = Time.local
+          if @@log_file
+            File.open(@@log_file, "a") do |file|
+              file.puts message
+            end
+          else
             STDERR.puts [time, level.to_s.colorize(_level.color), message].join(" : ")
+          end
           raise "ERROR : Fatal error detected (#{message})" if level == "FATAL"
       }
     end