Use fork of bloodhound to support ES 5.2

[akshaymankar]

Fixes https://github.com/zinfra/backend-issues/issues/1299

Branch on bloodhound fork: https://github.com/wireapp/bloodhound/tree/feature/count-with-ES-5.2

I don't plan on sending a PR for this as ES 5.2 is very old and we should just upgrade from it. There is already an issue for that: https://github.com/zinfra/backend-issues/issues/1161

[fisx]

this looks... manageable. :)

$ git diff upstream/master..origin/feature/count-with-ES-5.2
diff --git a/src/Database/Bloodhound/Internal/Count.hs b/src/Database/Bloodhound/Internal/Count.hs
index d2f732a..422ee84 100644
--- a/src/Database/Bloodhound/Internal/Count.hs
+++ b/src/Database/Bloodhound/Internal/Count.hs
@@ -29,7 +29,6 @@ instance FromJSON CountResponse where
 
 data CountShards = CountShards { csTotal      :: Int
                                , csSuccessful :: Int
-                               , csSkipped    :: Int
                                , csFailed     :: Int
                                }
   deriving (Eq, Show)
@@ -41,5 +40,4 @@ instance FromJSON CountShards where
         CountShards
         <$> o .: "total"
         <*> o .: "successful"
-        <*> o .: "skipped"
         <*> o .: "failed"