ci: add node-14.x to workflow (#108)

diff --git a/.travis.yml b/.travis.yml
index b0d2ab8..8acaeb1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,6 +6,7 @@
   matrix:
     - TRAVIS_NODE_VERSION: 10
     - TRAVIS_NODE_VERSION: 12
+    - TRAVIS_NODE_VERSION: 14
 
 before_install:
   - nvm install $TRAVIS_NODE_VERSION