title: Chart Title for Chart using python-pptx
body: <p>I am trying to add a title to my powerpoint chart created using <code>python-pptx</code> library. I am on OSX with Python 2.7 and Python pptx version 0.6.1. </p>
  
  <p>The code to create the charts is below : </p>
  
  <pre><code>df = pd.read_excel("/Users/vagabond/Documents/python_pptx_3/Bar_Charts.xlsx", sheetname=None)
  f = open('/Users/vagabond/Documents/python_pptx_3/Presentation1.pptx')
  prs = ppt.Presentation(f)
  
  for sheetname, data in df.iteritems():
  
      slide_layout = prs.slide_layouts[9]
      slide = prs.slides.add_slide(slide_layout)
  
      chart_data = ppt.chart.data.XyChartData()
  
      series_1 = chart_data.add_series('Series 1')
  
      ## iterate through rows of the data frame for desired columns and add data points
      for index, row in data.iterrows():
          series_1.add_data_point(row['Share_of_apples'], row['Share_of_oranges'])
  
      ## define co-ordinates on the slide
      x, y, cx, cy = Inches(1), Inches(3), Inches(7), Inches(4)
  
      chart = slide.shapes.add_chart(
      XL_CHART_TYPE.XY_SCATTER, x, y, cx, cy, chart_data
  ).chart
  
      prs.save('scatter_charts.pptx')
  </code></pre>
  
  <p>Now to add a title, I added the following after the <code>slide.shapes.add_chart</code> call: </p>
  
  <pre><code>chart.has_title = True
  chart.title = sheetname
  </code></pre>
  
  <p>In case you are wondering, the value sheetname in <code>chart.title = sheetname</code> are the dict keys of dict df which I read in the first line. For every chart , I want the key of the key-value pair in the dictionary to be assigned. The program runs without any error.</p>
  
  <p>The problem is , it does not add any chart titles. </p>
  
  <p>I checked if chart.chart_title contains any value and it gives me an error: </p>
  
  <pre><code>---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-26-7cb6c1e79da2&gt; in &lt;module&gt;()
        1 chart.has_title = True
        2 
  ----&gt; 3 chart.chart_title.has_text_frame = True
  
  AttributeError: 'Chart' object has no attribute 'chart_title'
  </code></pre>