Relax constraints, allow containers 0.6.*

Author: DanBurton

stylish-haskell.cabal

@@ -52,7 +52,7 @@ Library
     aeson            >= 0.6    && < 1.4,
     base             >= 4.8    && < 5,
     bytestring       >= 0.9    && < 0.11,
-    containers       >= 0.3    && < 0.6,
+    containers       >= 0.3    && < 0.7,
     directory        >= 1.2.3  && < 1.4,
     filepath         >= 1.1    && < 1.5,
     file-embed       >= 0.0.10 && < 0.1,
@@ -75,7 +75,7 @@ Executable stylish-haskell
     aeson            >= 0.6    && < 1.4,
     base             >= 4.8    && < 5,
     bytestring       >= 0.9    && < 0.11,
-    containers       >= 0.3    && < 0.6,
+    containers       >= 0.3    && < 0.7,
     directory        >= 1.2.3  && < 1.4,
     filepath         >= 1.1    && < 1.5,
     file-embed       >= 0.0.10 && < 0.1,
@@ -124,7 +124,7 @@ Test-suite stylish-haskell-tests
     aeson            >= 0.6    && < 1.4,
     base             >= 4.8    && < 5,
     bytestring       >= 0.9    && < 0.11,
-    containers       >= 0.3    && < 0.6,
+    containers       >= 0.3    && < 0.7,
     directory        >= 1.2.3  && < 1.4,
     filepath         >= 1.1    && < 1.5,
     file-embed       >= 0.0.10 && < 0.1,