Removed blaze_html_0_5 flag, require blaze-html >= 0.5.

Reason:  < 0.5 does not provide a monoid instance for Attribute,
which is now needed by the HTML writer.

Closes #803.

pandoc.cabal

@@ -215,9 +215,6 @@ Source-repository head
   type:          git
   location:      git://github.com/jgm/pandoc.git
 
-Flag blaze_html_0_5
-  Description:   Use blaze-html >= 0.5 and blaze-markup >= 0.5
-  Default:       True
 Flag embed_data_files
   Description:   Embed data files in binary for relocatable executable.
   Default:       False
@@ -250,14 +247,9 @@ Library
                  zlib >= 0.5 && < 0.6,
                  highlighting-kate >= 0.5.3.7 && < 0.6,
                  data-default >= 0.4 && < 0.6,
-                 temporary >= 1.1 && < 1.2
-  if flag(blaze_html_0_5)
-    build-depends:
+                 temporary >= 1.1 && < 1.2,
                  blaze-html >= 0.5 && < 0.7,
                  blaze-markup >= 0.5.1 && < 0.6
-  else
-    build-depends:
-                 blaze-html >= 0.4.3.0 && < 0.5
   if flag(embed_data_files)
      cpp-options:   -DEMBED_DATA_FILES
      -- build-tools:   hsb2hs

src/Text/Pandoc/Writers/HTML.hs

@@ -47,12 +47,8 @@ import Data.List ( isPrefixOf, intersperse )
 import Data.String ( fromString )
 import Data.Maybe ( catMaybes )
 import Control.Monad.State
-#if MIN_VERSION_blaze_html(0,5,0)
 import Text.Blaze.Html hiding(contents)
 import Text.Blaze.Internal(preEscapedString)
-#else
-import Text.Blaze
-#endif
 #if MIN_VERSION_blaze_html(0,5,1)
 import qualified Text.Blaze.XHtml5 as H5
 #else