Merge branch 'master' of github.com:masayuki0812/c3

bower.json

@@ -1,7 +1,7 @@
 {
   "name": "c3",
   "main": "c3.min.js",
-  "version": "0.1.30",
+  "version": "0.1.31",
   "homepage": "https://github.com/masayuki0812/c3",
   "authors": [
     "Masayuki Tanaka <masayuki0812@mac.com>"

c3.js

@@ -2,7 +2,7 @@
     'use strict';
 
     var c3 = {
-        version: "0.1.30"
+        version: "0.1.31"
     };
 
     var CLASS = {
@@ -173,7 +173,7 @@
             __axis_x_tick_culling_max = getConfig(['axis', 'x', 'tick', 'culling', 'max'], 10),
             __axis_x_tick_count = getConfig(['axis', 'x', 'tick', 'count']),
             __axis_x_tick_fit = getConfig(['axis', 'x', 'tick', 'fit'], false),
-            __axis_x_tick_values = getConfig(['axis', 'x', 'tick', 'values'], []),
+            __axis_x_tick_values = getConfig(['axis', 'x', 'tick', 'values'], null),
             __axis_x_max = getConfig(['axis', 'x', 'max']),
             __axis_x_min = getConfig(['axis', 'x', 'min']),
             __axis_x_default = getConfig(['axis', 'x', 'default']),

package.json

@@ -1,6 +1,6 @@
 {
   "name": "c3",
-  "version": "0.1.30",
+  "version": "0.1.31",
   "description": "D3-based reusable chart library",
   "main": "c3.js",
   "scripts": {