Merge pull request fluent-ffmpeg#937 from adityapatadia/patch-1

updated node version to 12

Author: njoyard

.travis.yml

@@ -10,7 +10,7 @@ jobs:
     - os: linux
       env: NODE_VERSION=10
     - os: linux
-      env: NODE_VERSION=11
+      env: NODE_VERSION=12
 
 script:
   - tools/test-travis.sh