Added 21Sextury scraper. Various improvements.

src/scrapers/index.js

@@ -9,10 +9,12 @@ const legalporno = require('./legalporno');
 const mofos = require('./mofos');
 const pervcity = require('./pervcity');
 const privateNetwork = require('./private'); // reserved keyword
+const twentyonesextury = require('./21sextury');
 const vixen = require('./vixen');
 const xempire = require('./xempire');
 
 module.exports = {
+    '21sextury': twentyonesextury,
     blowpass,
     brazzers,
     ddfnetwork,