Fix issue with nats package update for ghc-7.6 and ghc-7.8

ihaskell-display/ihaskell-widgets/ihaskell-widgets.cabal

@@ -96,34 +96,25 @@ library
   
   -- Other library packages from which modules are imported.
   -- singletons 2.* require ghc 7.10.2
-  if impl(ghc >= 7.10.2)  
-    build-depends:       aeson >=0.7 && < 0.11
-                       , base >=4.7 && <4.9
-                       , containers >= 0.5
-                       , ipython-kernel >= 0.6.1.2
-                       , text >= 0.11
-                       , unordered-containers -any
+  build-depends:       aeson >=0.7 && < 0.11
+                     , base >=4.7 && <4.9
+                     , containers >= 0.5
+                     , ipython-kernel >= 0.6.1.2
+                     , text >= 0.11
+                     , unordered-containers -any
+                     , vinyl >= 0.5
+                     , vector -any
+                     , scientific -any
+                     , unix -any
+                     , ihaskell >= 0.6.4.1
+  if impl(ghc >= 7.10.2)
+    build-depends:       singletons >= 0.9.0
+  if impl(ghc == 7.10.1)
+    build-depends:       singletons >= 0.9.0 && <2.0
                        , nats -any
-                       , vinyl >= 0.5
-                       , vector -any
-                       , singletons >= 0.9.0 
-                       , scientific -any
-                       , unix -any
-                       , ihaskell >= 0.6.4.1
-  else
-    build-depends:       aeson >=0.7 && < 0.11
-                       , base >=4.7 && <4.9
-                       , containers >= 0.5
-                       , ipython-kernel >= 0.6.1.2
-                       , text >= 0.11
-                       , unordered-containers -any
-                       , nats -any
-                       , vinyl >= 0.5
-                       , vector -any
-                       , singletons >= 0.9.0 && <2.0
-                       , scientific -any
-                       , unix -any
-                       , ihaskell >= 0.6.4.1
+  if impl(ghc < 7.10.1)
+    build-depends:       singletons >= 0.9.0 && <2.0
+                       , nats <1.1
   
   -- Directories containing source files.
   hs-source-dirs:      src