Add lambda snippet

Author: Shougo

neosnippets/haskell.snip

@@ -30,3 +30,8 @@ snippet     instance
 options     head
   instance ${1:Class} ${2:Type} where
     ${3:function} ${4:self} = ${0:TARGET}
+
+snippet     lambda
+abbr        λ
+  \ ${1:x} -> ${0}
+