Bump to kotlin 1.2.0

Author: sys1yagi

build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.1.4'
+    ext.kotlin_version = '1.2.0'
     ext.supportTestVersion = '0.5'
     ext.okhttpVersion = '3.6.0'
     ext.gradleToolsVersion = '2.3.1'
@@ -37,8 +37,8 @@ subprojects {
     apply plugin: 'java'
     apply plugin: 'maven'
 
-    sourceCompatibility = 1.7
-    targetCompatibility = 1.7
+    sourceCompatibility = 1.8
+    targetCompatibility = 1.8
 
     task sourcesJar(type: Jar, dependsOn: classes) {
         classifier = 'sources'