Add partially integrated BitbucketCrawler().

Add:
    bitshift/crawler/
        __init__.py
            -Initialize 'BitbucketCrawler()' singleton.
            -Instantiate all thread instances on-the-fly in a 'threads' array, as
            opposed to individual named variables.

        crawler.py
            -Add 'BitbucketCrawler()', to crawl Bitbucket for repositories.
            -Not entirely tested for proper functionality.
            -The Bitbucket framework is not yet accounted for in
            'indexer._generate_file_url()'.

bitshift/crawler/crawler.py

@@ -15,14 +15,13 @@ class GitHubCrawler(threading.Thread):
     """
     Crawler that retrieves links to all of GitHub's public repositories.
 
-    GitHubCrawler is a threaded singleton that queries GitHub's API for URLs
+    GitHubCrawler is a threaded singleton that queries GitHub's API for urls
     to its public repositories, which it inserts into a :class:`Queue.Queue`
-    shared with :class:`bitshift.crawler.indexer.GitIndexer`.
+    shared with :class:`indexer.GitIndexer`.
 
     :ivar clone_queue: (:class:`Queue.Queue`) Contains :class:`GitRepository`
-        with repository metadata retrieved by :class:`GitHubCrawler`, and other
-        Git crawlers, to be processed by
-        :class:`bitshift.crawler.indexer.GitIndexer`.
+    with repository metadata retrieved by :class:`GitHubCrawler`, and other Git
+    crawlers, to be processed by :class:`indexer.GitIndexer`.
     """
 
     def __init__(self, clone_queue):
@@ -35,7 +34,7 @@ class GitHubCrawler(threading.Thread):
         """
 
         self.clone_queue = clone_queue
-        logging.info("Starting.")
+        logging.info("Starting %s." % self.__class__.__name__)
         super(GitHubCrawler, self).__init__(name=self.__class__.__name__)
 
     def run(self):
@@ -84,3 +83,64 @@ class GitHubCrawler(threading.Thread):
             sleep_time = api_request_interval - (time.time() - start_time)
             if sleep_time > 0:
                 time.sleep(sleep_time)
+
+class BitbucketCrawler(threading.Thread):
+    """
+    Crawler that retrieves links to all of Bitbucket's public repositories.
+
+    BitbucketCrawler is a threaded singleton that queries Bitbucket's API for
+    urls to its public repositories, and inserts them as
+    :class:`indexer.GitRepository` into a :class:`Queue.Queue` shared with
+    :class:`indexer.GitIndexer`.
+
+    :ivar clone_queue: (:class:`Queue.Queue`) The shared queue to insert
+        :class:`indexer.GitRepository` repository urls into.
+    """
+
+    def __init__(self, clone_queue):
+        """
+        Create an instance of the singleton `BitbucketCrawler`.
+
+        :param clone_queue: see :attr:`self.clone_queue`
+
+        :type clone_queue: see :attr:`self.clone_queue`
+        """
+
+        self.clone_queue = clone_queue
+        logging.info("Starting %s." % self.__class__.__name__)
+        super(BitbucketCrawler, self).__init__(name=self.__class__.__name__)
+
+    def run(self):
+        """
+        Query  the Bitbucket API for data about every public repository.
+
+        Query the Bitbucket API's "/repositories" endpoint and read its
+        paginated responses in a loop; any "git" repositories have their
+        clone-urls and names inserted into a :class:`indexer.GitRepository` in
+        :attr:`self.clone_queue`.
+        """
+
+        next_api_url = "https://api.bitbucket.org/2.0/repositories"
+
+        while True:
+            response = requests.get(next_api_url).json()
+
+            queue_percent_full = (float(self.clone_queue.qsize()) /
+                    self.clone_queue.maxsize) * 100
+            logging.info("API call made. Queue-size: (%d%%) %d/%d" % (
+                queue_percent_full, self.clone_queue.qsize(),
+                self.clone_queue.maxsize))
+
+            for repo in response["values"]:
+                if repo["scm"] == "git":
+                    while self.clone_queue.full():
+                        time.sleep(1)
+
+                    clone_links = repo["links"]["clone"]
+                    clone_url = (clone[0]["href"] if clone[0]["name"] == "https"
+                             else clone[1]["href"])
+                    links.append("clone_url")
+                    self.clone_queue.put(indexer.GitRepository(
+                        clone_url, repo["full_name"], "Bitbucket"))
+
+            next_api_url = response["next"]