Add pomodoro module.

Add _Pomodoro_ module. See http://en.wikipedia.org/wiki/Pomodoro_Technique
It uses `aplay` for playing alarm sound. It also uses `notify-send` utility
for nitification.

i3pystatus/pomodoro.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import os
+import subprocess
+import locale
+
+from datetime import datetime, timedelta
+
+from i3pystatus import IntervalModule
+
+
+class Pomodoro(IntervalModule):
+  """
+  This class shows a clock
+  """
+
+  settings = (
+    ('sound', 'Path to sound file to play as alarm. Played by "aplay" utility'),
+    ('pomodoro_duration', 'Working (pomodoro) interval duration in seconds'),
+    ('break_duration', 'Short break duration in secods'),
+    ('long_break_duration', 'Long break duration in secods'),
+    ('short_break_count', 'Short break count before first long break'),
+  )
+
+  color_stopped = '#2ECCFA'
+  color_running = '#FFFF00'
+  color_break = '#37FF00'
+  interval = 1
+  short_break_count = 3
+
+  pomodoro_duration = 25 * 60
+  break_duration = 5 * 60
+  long_break_duration = 15 * 60
+
+  def init(self):
+    # state could be either running/break or stopped
+    self.state = 'stopped'
+    self.breaks = 0
+    self.time = None
+
+  def run(self):
+    if self.time and datetime.now() >= self.time:
+      if self.state == 'running':
+        self.state = 'break'
+        if self.breaks == self.short_break_count:
+          self.time = datetime.now() + timedelta(seconds=self.long_break_duration)
+          self.breaks = 0
+        else:
+          self.time = datetime.now() + timedelta(seconds=self.break_duration)
+        text = 'Go for a break!'
+        self.breaks += 1
+      else:
+        self.state = 'running'
+        self.time = datetime.now() + timedelta(seconds=self.pomodoro_duration)
+        text = 'Back to work!'
+      self._alarm(text)
+
+    if self.state == 'running' or self.state == 'break':
+      min, sec = divmod((self.time - datetime.now()).total_seconds(), 60)
+      text = '{:02}:{:02}'.format(int(min), int(sec))
+      color = self.color_running if self.state == 'running' else self.color_break
+    else:
+      text = 'Stopped'
+      color = self.color_stopped
+
+    self.output = {
+        'full_text': text,
+        'color': color
+    }
+
+  def on_leftclick(self):
+    self.state = 'running'
+    self.time = datetime.now() + timedelta(seconds=self.pomodoro_duration)
+
+  def on_rightclick(self):
+    self.state = 'stopped'
+    self.time = None
+
+  def _alarm(self, text):
+    subprocess.call(['notify-send',
+                      'Alarm!',
+                      text])
+    subprocess.Popen(['aplay',
+                      self.sound,
+                      '-q'], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+