Restore support for building with kotlinSnapshot

Author: elizarov

build.gradle

@@ -3,6 +3,12 @@ allprojects {
 }
 
 buildscript {
+    if (System.properties['kotlinSnapshot'] != null) {
+        ext.kotlin_version = '1.1-SNAPSHOT'
+        repositories {
+            maven { url "https://oss.sonatype.org/content/repositories/snapshots" }
+        }
+    }
     repositories {
         jcenter()
     }