title: Python : How to make label bold in kivy
body: <p>I am using <code>Popup</code> widgets in <code>python-2.7</code> and <code>kivy</code>.Can someone help me?<br/>
  1. How to make label bold ? (ex. <code>text: "make label bold"</code>)<br/>
  2. How to change color of title ? (ex. <code>title : "change title color"</code>)</p>
  
  <h1>test.py</h1>
  
  <pre><code>from kivy.app import App
  from kivy.core.window import Window
  from kivy.uix.popup import Popup
  
  class abc(Popup):
      def __init__(self, **kwargs):
          super(abc, self).__init__(**kwargs)
          self.open()
  
  
  class TestApp(App):
      def build(self):
          return abc()
  
  
  TestApp().run()
  </code></pre>
  
  <h1>test.kv</h1>
  
  <pre><code>&lt;abc&gt;
      title : "change title color"
      BoxLayout:
          orientation: "vertical"
          GridLayout:
              Label:
                  text: "make label bold"
  </code></pre>