Update Kotlin to 1.1.2

Also switch to oraclejdk8 on Travis CI, as it is required for Kotlin
1.1.2 to build.

Author: xenomachina

.travis.yml

@@ -1,9 +1,11 @@
 language: java
 
+jdk:
+    - oraclejdk8
+
 before_cache:
     - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
     - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
 cache:
     directories:
-        - $HOME/.gradle/caches/
-        - $HOME/.gradle/wrapper/
+        - $HOME/.gradle/

gradle.properties

@@ -3,6 +3,6 @@ version=2.0.1-SNAPSHOT
 # Dependency versions
 dokka_version = 0.9.13
 kotlintest_version = 2.0.1
-kotlin_version = 1.1.1
+kotlin_version = 1.1.2
 ktlint_version = 0.6.1
 xenocom_version = 0.0.4