Fix nasty module graph caching issue

resolvedComponentsCache did not consider outgoing edges in the module
graph when computing the set of dependent files

i.e. for `A -> B, A -> C` `flatten` would give [B,C] instead of [A,B,C]

Language/Haskell/GhcMod/Caching/Types.hs

@@ -47,6 +47,6 @@ data TimedCacheFiles = TimedCacheFiles {
   -- ^ 'cacheFile' timestamp
   tcFiles     :: [TimedFile]
   -- ^ Timestamped files returned by the cached action
- }
+ } deriving (Eq, Ord, Show)
 
 type ChCacheData = (Programs, FilePath, FilePath, (Version, [Char]))