Remove memcached support

Apparently we had memcached support. It was never worth it, and put
a weird md5 hash calculation in the path of regular caching. Seeing
as it was completely undocumented, I doubt anyone has ever used it.

overviewer_core/cache.py

@@ -22,7 +22,6 @@ attribute.
 """
 import functools
 import logging
-import cPickle
 
 class LRUCache(object):
     """A simple, generic, in-memory LRU cache that implements the standard
@@ -137,31 +136,3 @@ class LRUCache(object):
         d = self.destructor
         if d:
             d(link.value)
-
-# memcached is an option, but unless your IO costs are really high, it just
-# ends up adding overhead and isn't worth it.
-try:
-    import memcache
-except ImportError:
-    class Memcached(object):
-        def __init__(*args):
-            raise ImportError("No module 'memcache' found. Please install python-memcached")
-else:
-    class Memcached(object):
-        def __init__(self, conn='127.0.0.1:11211'):
-            self.conn = conn
-            self.mc = memcache.Client([conn], debug=0, pickler=cPickle.Pickler, unpickler=cPickle.Unpickler)
-
-        def __getstate__(self):
-            return self.conn
-        def __setstate__(self, conn):
-            self.__init__(conn)
-
-        def __getitem__(self, key):
-            v = self.mc.get(key)
-            if not v:
-                raise KeyError()
-            return v
-
-        def __setitem__(self, key, value):
-            self.mc.set(key, value)