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/__init__.py

@@ -15,20 +15,22 @@ def crawl():
     Initialize all crawlers (and indexers).
 
     Start the:
-    1. GitHub crawler, :class:`bitshift.crawler.crawler.GitHubCrawler`
-    2. Git indexer, :class:`bitshift.crawler.indexer.GitIndexer`
+    1. GitHub crawler, :class:`crawler.GitHubCrawler`.
+    2. Bitbucket crawler, :class:`crawler.BitbucketCrawler`.
+    3. Git indexer, :class:`bitshift.crawler.indexer.GitIndexer`.
     """
 
     MAX_URL_QUEUE_SIZE = 5e3
     DEBUG_FILE = "crawler.log"
 
     logging.basicConfig(filename=DEBUG_FILE,
-            format="%(asctime)s:\t%(threadName)s:\t%(message)s",
+            format="%(levelname)s %(asctime)s:\t%(threadName)s:\t%(message)s",
             level=logging.DEBUG)
 
-    repository_queue = Queue.Queue(maxsize=MAX_URL_QUEUE_SIZE)
-    github_crawler = crawler.GitHubCrawler(repository_queue)
-    git_indexer = indexer.GitIndexer(repository_queue)
+    repo_clone_queue = Queue.Queue(maxsize=MAX_URL_QUEUE_SIZE)
+    threads = [crawler.GitHubCrawler(repo_clone_queue),
+            crawler.BitbucketCrawler(repo_clone_queue),
+            indexer.GitIndexer(repo_clone_queue)]
 
-    for thread in [github_crawler, git_indexer]:
+    for thread in threads:
         thread.start()