update github engine and add comments

searx/engines/github.py

+## Github (It)
+# 
+# @website     https://github.com/
+# @provide-api yes (https://developer.github.com/v3/)
+# 
+# @using-api   yes
+# @results     JSON
+# @stable      yes (using api)
+# @parse       url, title, content
+
 from urllib import urlencode
 from json import loads
 from cgi import escape
 
+# engine dependent config
 categories = ['it']
 
+# search-url
 search_url = 'https://api.github.com/search/repositories?sort=stars&order=desc&{query}'  # noqa
 
 accept_header = 'application/vnd.github.preview.text-match+json'
 
 
+# do search-request
 def request(query, params):
     params['url'] = search_url.format(query=urlencode({'q': query}))
+
     params['headers']['Accept'] = accept_header
+
     return params
 
 
+# get response from search-request
 def response(resp):
     results = []
+
     search_res = loads(resp.text)
+
+    # check if items are recieved
     if not 'items' in search_res:
-        return results
+        return []
+
+    # parse results
     for res in search_res['items']:
         title = res['name']
         url = res['html_url']
+
         if res['description']:
             content = escape(res['description'][:500])
         else:
             content = ''
-        results.append({'url': url, 'title': title, 'content': content})
+
+        # append result
+        results.append({'url': url,
+                        'title': title,
+                        'content': content})
+
+    # return results
     return results

searx/settings.yml

 
   - name : github
     engine : github
-    categories : it
     shortcut : gh
 
   - name : google