Fix french zéro

Author: forzagreen

lib/i18n/fr.json

@@ -3,7 +3,7 @@
   "baseSeparator": "-",
   "unitSeparator": "",
   "base": {
-    "0": "zero",
+    "0": "zéro",
     "1": "un",
     "2": "deux",
     "3": "trois",

test/index.test.js

@@ -235,6 +235,7 @@ describe("written-number", function() {
     });
 
     it("correctly converts numbers < 10", function() {
+      writtenNumber(0).should.equal("zéro");
       writtenNumber(3).should.equal("trois");
       writtenNumber(8).should.equal("huit");
     });