make hledger-web installable with GHC < 7.6 again

Revisiting the "directory 1.2 can be installed with older GHC, so we'd better pin it in the cabal file" change.
Requiring directory 1.2 made hledger-web uninstallable with GHC < 7.6 because current yesod depends on ghc
which depends on a particular directory version and can't be upgraded. This is a smarter fix, which should let
all hledger packages build with whatever directory version is installed.

hledger/Hledger/Cli/Utils.hs

@@ -1,4 +1,4 @@
-{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE ScopedTypeVariables, CPP #-}
 {-|
 
 Utilities for top-level modules and ghci. See also Hledger.Read and
@@ -34,8 +34,10 @@ import System.Process (readProcessWithExitCode)
 import System.Time (ClockTime, getClockTime, diffClockTimes, TimeDiff(TimeDiff))
 import Test.HUnit
 import Text.Printf
+#if MIN_VERSION_directory(1,2,0)
 import System.Time (ClockTime(TOD))
 import Data.Time.Clock.POSIX (utcTimeToPOSIXSeconds)
+#endif
 
 import Hledger.Cli.Options
 import Hledger.Data
@@ -101,9 +103,13 @@ fileModificationTime :: FilePath -> IO ClockTime
 fileModificationTime f
     | null f = getClockTime
     | otherwise = (do
+#if MIN_VERSION_directory(1,2,0)
         utc <- getModificationTime f
         let nom = utcTimeToPOSIXSeconds utc
         let clo = TOD (read $ takeWhile (`elem` "0123456789") $ show nom) 0 -- XXX read
+#else
+        clo <- getModificationTime f
+#endif
         return clo
         )
         `C.catch` \(_::C.IOException) -> getClockTime

hledger/hledger.cabal

@@ -67,7 +67,7 @@ library
                  -- ,cabal-file-th
                  ,containers
                  ,cmdargs >= 0.10 && < 0.11
-                 ,directory >= 1.2
+                 ,directory
                  ,filepath
                  ,haskeline >= 0.6 && <= 0.8
                  ,HUnit
@@ -120,7 +120,7 @@ executable hledger
                  ,base >= 4.3 && < 5
                  ,containers
                  ,cmdargs >= 0.10 && < 0.11
-                 ,directory >= 1.2
+                 ,directory
                  ,filepath
                  ,haskeline >= 0.6 && <= 0.8
                  ,HUnit