Surrounds BLOG_NAME with try/catch rather than getattr.

Fixes "DatabaseError: no such table: django_site" issue, refs pigmonkey#3

Author: AndreMiras

vellum/settings.py

@@ -7,7 +7,10 @@
 
 # The name of the blog.
 # This defaults to the name of the site.
-BLOG_NAME = getattr(settings, 'BLOG_NAME', Site.objects.get_current().name)
+try:
+    BLOG_NAME = settings.BLOG_NAME
+except ValueError:
+    BLOG_NAME = Site.objects.get_current().name
 
 # A short description of what the blog is about.
 BLOG_DESCRIPTION = getattr(settings, 'BLOG_DESCRIPTION', 'A basic Django blog')