Merge pull request #350 from serverless-operations/deprecate_node8

ci: updated .travis.yml

Author: horike37

.travis.yml

@@ -2,7 +2,6 @@ language: node_js
 
 matrix:
   include:
-    - node_js: 8
     - node_js: 10
     - node_is: 12
     - node_js: 12
@@ -23,4 +22,4 @@ script:
 after_success:
   - codecov
   - rm -rf ./.nyc_output
-  - rm -rf ./coverage
+  - rm -rf ./coverage