Add btdigg backend

A resubmit of the previous one, this time with understandable name.
Copied the original submission text.

This is a simple backend for btdigg.org. This site is especially
interesting because it is not an indexer where uploaders add their
torrents; it crawls the DHT and listens to all infohashes being
exchanged by the nodes.

Because of this, btdigg.org provides no description and no torrent
files, only magnets. Moreover, there are no seeders and leechers
(although there is the number of peers in the swarms)

Note that there is no icon.

Signed-off-by: Matthieu Rakotojaona <matthieu.rakotojaona@gmail.com>
Signed-off-by: Romain Bignon <romain@symlink.me>

modules/bitedick/test.py

@@ -0,0 +1,43 @@
+# -*- coding: utf-8 -*-
+
+from weboob.tools.test import BackendTest
+from weboob.capabilities.torrent import MagnetOnly
+
+from random import choice
+
+__all__ = ['BTDiggTest']
+
+class BTDiggTest(BackendTest):
+    BACKEND = 'btdigg'
+
+    def test_iter_torrents(self):
+        # try something popular so we sometimes get a magnet-only torrent
+        l = list(self.backend.iter_torrents('ubuntu linux'))
+        self.assertTrue(len(l) == 10)
+        for torrent in l:
+            assert torrent.name
+            assert torrent.url
+            assert torrent.size
+            assert torrent.magnet
+            assert torrent.date
+
+            self.assertEquals(40, len(torrent.id))
+
+    def test_get_random_torrentfile(self):
+        torrent = choice(list(self.backend.iter_torrents('ubuntu linux')))
+        full_torrent = self.backend.get_torrent(torrent.id)
+        try:
+            self.backend.get_torrent_file(torrent.id)
+        except MagnetOnly as e:
+            assert e.magnet.startswith("magnet:")
+            assert e.magnet == full_torrent.magnet
+
+    def test_get_special_torrent(self):
+        torrent = self.backend.get_torrent("c2e018a16bf28520687e400580be08934d00373a")
+        assert torrent.name == u'Ubuntu Linux Toolbox - 1000+ Commands for Ubuntu and Debian Power Users~tqw~_darksiderg'
+        assert len(torrent.files) == 3
+        assert torrent.size == float(3376414.72)
+        assert torrent.url == "https://btdigg.org/search?info_hash=c2e018a16bf28520687e400580be08934d00373a"
+        dt = torrent.date
+        assert dt.year == 2011
+        assert dt.month == 2