fixing throwing an error string in the Rewriter, when it should have been an Error object

examples/blocks.coffee

@@ -8,7 +8,7 @@ get '/hello', ->
 # Append.
 append: (location, data) ->
   path: new Pathname location
-  throw "Location does not exist" unless path.exists()
+  throw new Error("Location does not exist") unless path.exists()
 
   File.open path, 'a', (file) ->
     file.puts YAML.dump data

lib/rewriter.js

@@ -295,7 +295,7 @@
             levels[open] -= 1;
           }
           if (levels[open] < 0) {
-            throw "too many " + token[1];
+            throw new Error("too many " + token[1]);
           }
         }
         return 1;

src/rewriter.coffee

@@ -199,7 +199,7 @@ re::ensure_balance: (pairs) ->
       levels[open] ||= 0
       levels[open] += 1 if token[0] is open
       levels[open] -= 1 if token[0] is close
-      throw "too many " + token[1] if levels[open] < 0
+      throw new Error("too many " + token[1]) if levels[open] < 0
     return 1
   unclosed: key for key, value of levels when value > 0
   throw new Error("unclosed " + unclosed[0]) if unclosed.length