[enh] wikipedia search added

searx/engines/wikipedia.py

+from json import loads
+
+def request(query, params):
+    params['url'] = 'http://en.wikipedia.org/w/api.php?action=query&list=search&srsearch=%s&srprop=timestamp&format=json' % query
+
+    return params
+
+
+def response(resp):
+    search_results = loads(resp.text)
+    results = []
+    for res in search_results.get('query', {}).get('search', []):
+        results.append({'url': 'https://en.wikipedia.org/wiki/%s' % res['title'], 'title': res['title']})
+    return results
+