diff --git a/build.gradle b/build.gradle
index d551131f..ef3aeb13 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,10 +1,28 @@
 buildscript {
+    ext {
+        aliyunMavenUrl = "http://maven.aliyun.com/nexus/content/groups/public"
+        jacksonVersion = "2.8.9"
+        junitJupiterVersion = "5.0.0-M4"
+        junitPlatformVersion = "1.0.0-M4"
+        kotlinVersion = "1.1.3"
+        spekVersion = "1.1.2"
+
+        if (project.rootProject.file("private.properties").exists()) {
+            Properties properties = new Properties()
+            properties.load(project.rootProject.file("private.properties").newDataInputStream())
+            bintrayUserProperty = properties.getProperty("bintrayUser")
+            bintrayKeyProperty = properties.getProperty("bintrayKey")
+        } else {
+            bintrayUserProperty = ""
+            bintrayKeyProperty = ""
+        }
+    }
     repositories {
-        //maven { url "http://maven.aliyun.com/nexus/content/groups/public" }
+        //maven { url aliyunMavenUrl }
         jcenter()
     }
     dependencies {
-        classpath "org.junit.platform:junit-platform-gradle-plugin:1.0.0-M4"
+        classpath "org.junit.platform:junit-platform-gradle-plugin:$junitPlatformVersion"
         classpath "com.novoda:bintray-release:0.5.0"
         classpath "org.jetbrains.dokka:dokka-gradle-plugin:0.9.15"
     }
@@ -28,27 +46,9 @@ apply plugin: "org.jetbrains.dokka"
 group "com.uchuhimo"
 version "0.1"
 
-ext {
-    junitJupiterVersion = "5.0.0-M4"
-    kotlinVersion = "1.1.3"
-    spekVersion = "1.1.2"
-    jacksonVersion = "2.8.9"
-
-    if (project.rootProject.file("private.properties").exists()) {
-        Properties properties = new Properties()
-        properties.load(project.rootProject.file("private.properties").newDataInputStream())
-        bintrayUserProperty = properties.getProperty("bintrayUser")
-        bintrayKeyProperty = properties.getProperty("bintrayKey")
-    } else {
-        bintrayUserProperty = ""
-        bintrayKeyProperty = ""
-    }
-}
-
 repositories {
-    //maven { url "http://maven.aliyun.com/nexus/content/groups/public" }
+    //maven { url aliyunMavenUrl }
     jcenter()
-    maven { url 'https://jitpack.io' }
 }
 
 task wrapper(type: Wrapper) {
@@ -59,7 +59,7 @@ task wrapper(type: Wrapper) {
 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlinVersion"
     compile "org.jetbrains.kotlin:kotlin-reflect:$kotlinVersion"
-    compile "com.github.uchuhimo:kotlinx-bimap:v0.2"
+    compile "com.uchuhimo:kotlinx-bimap:0.2"
     compile "com.typesafe:config:1.3.1"
     compile "com.fasterxml.jackson.core:jackson-core:$jacksonVersion"
     compile "com.fasterxml.jackson.core:jackson-annotations:$jacksonVersion"
@@ -72,7 +72,7 @@ dependencies {
 
     testCompile "com.natpryce:hamkrest:1.4.0.0"
     testCompile "org.hamcrest:hamcrest-all:1.3"
-    testRuntime "org.junit.platform:junit-platform-launcher:1.0.0-M4"
+    testRuntime "org.junit.platform:junit-platform-launcher:$junitPlatformVersion"
     testCompile "org.junit.jupiter:junit-jupiter-api:$junitJupiterVersion"
     testRuntime "org.junit.jupiter:junit-jupiter-engine:$junitJupiterVersion"
     ["spek-api", "spek-data-driven-extension", "spek-subject-extension"].each {