title: Scraping table with subscript <sub> data
body: <p>I'm currently having fun with scrapy and Python 3.6. My goal is to scrape all data from table with such html code:</p>
  
  <pre><code>&lt;table class="table table-a"&gt;
                      &lt;tbody&gt;&lt;tr&gt;
                          &lt;td colspan="2"&gt;
                              &lt;h2 class="text-center no-margin"&gt;Geometry&lt;/h2&gt;
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Depth of section"&gt;h = 267 mm&lt;/td&gt;
                          &lt;td rowspan="8" class="text-center"&gt;
                              &lt;a href="http://www.staticstools.eu/assets/image/profile-ipea.png" target="_blank"&gt;
                                  &lt;img src="http://www.staticstools.eu/assets/image/profile-ipea-thumb.png" alt="Section IPEA" class="img-responsive"&gt;
                              &lt;/a&gt;
                          &lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Width of section"&gt;b = 135 mm&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Flange thickness"&gt;t&lt;sub&gt;f&lt;/sub&gt; = 8.7 mm&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Web thickness"&gt;t&lt;sub&gt;w&lt;/sub&gt; = 5.5 mm&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Radius of root fillet"&gt;r&lt;sub&gt;1&lt;/sub&gt; = 15 mm&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Distance of centre of gravity along y-axis"&gt;y&lt;sub&gt;s&lt;/sub&gt; = 67.5 mm&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Depth of straight portion of web"&gt;d = 219.6 mm&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Area of section"&gt;A = 3915 mm&lt;sup&gt;2&lt;/sup&gt;&lt;/td&gt;
                      &lt;/tr&gt;
                      &lt;tr&gt;
                          &lt;td title="Painting surface per unit lenght"&gt;A&lt;sub&gt;L&lt;/sub&gt; = 1.04 m&lt;sup&gt;2&lt;/sup&gt;.m&lt;sup&gt;-1&lt;/sup&gt;&lt;/td&gt;
                          &lt;td title="Mass per unit lenght"&gt;G = 30.7 kg.m&lt;sup&gt;-1&lt;/sup&gt;&lt;/td&gt;
                      &lt;/tr&gt;
                  &lt;/tbody&gt;&lt;/table&gt;
  </code></pre>
  
  <p>In some rows I'm facing with <code>&lt;sup&gt;</code> and <code>&lt;sub&gt;</code> index formatting which makes everything harder. What I mean is, by using:</p>
  
  <pre><code>response.css('table.table.table-a td::text').extract()
  </code></pre>
  
  <p>Output is:</p>
  
  <pre><code>['\n                            ',
   '\n                        ',
   'h = 267 mm',
   '\n                            ',
   '\n                        ',
   'b = 135 mm',
   't',
   ' = 8.7 mm',
   't',
   ' = 5.5 mm',
   'r',
   ' = 15 mm',
   'y',
   ' = 67.5 mm',
   'd = 219.6 mm',
   'A = 3915 mm',
   'A',
   ' = 1.04 m',
   '.m',
   'G = 30.7 kg.m']
  </code></pre>
  
  <p>So everything is messed a bit. I can also include nested tags using:</p>
  
  <pre><code>response.css('table.table.table-a td *::text').extract()
  </code></pre>
  
  <p>with output as such:</p>
  
  <pre><code>['\n                            ',
   'Geometry',
   '\n                        ',
   'h = 267 mm',
   '\n                            ',
   '\n                                ',
   '\n                            ',
   '\n                        ',
   'b = 135 mm',
   't',
   'f',
   ' = 8.7 mm',
   't',
   'w',
   ' = 5.5 mm',
   'r',
   '1',
   ' = 15 mm',
   'y',
   's',
   ' = 67.5 mm',
   'd = 219.6 mm',
   'A = 3915 mm',
   '2',
   'A',
   'L',
   ' = 1.04 m',
   '2',
   '.m',
   '-1',
   'G = 30.7 kg.m',
   '-1']
  </code></pre>
  
  <p>I can of course post-process that data for some tweeking, but I was wondering if it's possible to achieve it during scraping? I want my output data to be as follows:</p>
  
  <pre><code> ['h = 267 mm',
       'b = 135 mm',
       'tf = 8.7 mm',
       'tw = 5.5 mm',
       'r1 = 15 mm', 
       'ys = 67.5 mm',
       'd = 219.6 mm',
       'A = 3915 mm2',
       'AL = 1.04 m2.m-1',
       'G = 30.7 kg.m-1']
  </code></pre>