Add support to kotlin 1.2.30 to the toolchains. (#43)

* Add support to kotlin 1.2.30 to the toolchains.

* Bump the current/default version.
diff --git a/kotlin/kotlin_compiler_repositories.bzl b/kotlin/kotlin_compiler_repositories.bzl
index 2531073..741dfa6 100644
--- a/kotlin/kotlin_compiler_repositories.bzl
+++ b/kotlin/kotlin_compiler_repositories.bzl
@@ -20,6 +20,11 @@
 )
 
 KOTLIN_RELEASES = {
+    "1.2.30": {
+        "version": "1.2.30",
+        "url": "https://github.com/JetBrains/kotlin/releases/download/v1.2.30/kotlin-compiler-1.2.30.zip",
+        "sha256": "4d6965877301d44241ca6de36480140992dc8a6b1c1884baeb5239ce2c43e071",
+    },
     "1.2.21": {
         "version": "1.2.21",
         "url": "https://github.com/JetBrains/kotlin/releases/download/v1.2.21/kotlin-compiler-1.2.21.zip",
@@ -142,7 +147,7 @@
 exports_files(["src"])
 """
 
-KOTLIN_CURRENT_RELEASE = "1.2.21"
+KOTLIN_CURRENT_RELEASE = "1.2.30"
 
 _BAZEL_JAVA_LAUNCHER_VERSION = "0.8.1"