Add additional GHC versions to CI (GHC-8.2, GHC-8.4)

Author: kvanbere

.travis.yml

@@ -13,6 +13,10 @@ matrix:
       env: STACK_YAML=stack-ghc-7.10.yaml STACK_PKG_URL=https://www.stackage.org/stack/linux-x86_64
     - os: linux
       env: STACK_YAML=stack-ghc-8.0.yaml STACK_PKG_URL=https://www.stackage.org/stack/linux-x86_64
+    - os: linux
+      env: STACK_YAML=stack-ghc-8.2.yaml STACK_PKG_URL=https://www.stackage.org/stack/linux-x86_64
+    - os: linux
+      env: STACK_YAML=stack-ghc-8.4.yaml STACK_PKG_URL=https://www.stackage.org/stack/linux-x86_64
     # Current releases
     - os: linux
       env: STACK_PKG_URL=https://www.stackage.org/stack/linux-x86_64

stack-ghc-8.2.yaml

@@ -0,0 +1 @@
+resolver: lts-11.22

stack-ghc-8.4.yaml

@@ -0,0 +1 @@
+resolver: lts-12.26