travis: remove chakracore on travis

1. node-chakracore v8 doesn’t expose napi version
2. node-chakracore v10 doesn’t throws on handlescope double escape
3. set npm_config_NAPI_VERSION to override NAPI_EXPERIMENTAL expansion

.travis.yml

@@ -12,20 +12,12 @@ env:
     # https://github.com/jasongin/nvs/blob/master/doc/CI.md
     - NVS_VERSION=1.4.2
   matrix:
-    - NODEJS_VERSION=node/4
-    - NODEJS_VERSION=node/6
-    - NODEJS_VERSION=node/8
-    - NODEJS_VERSION=node/9
-    - NODEJS_VERSION=node/10
-    - NODEJS_VERSION=chakracore/8
-    - NODEJS_VERSION=chakracore/10
-    - NODEJS_VERSION=nightly
-    - NODEJS_VERSION=chakracore-nightly
+    - NODEJS_VERSION=node/6 NAPI_VERSION=3
+    - NODEJS_VERSION=node/8 NAPI_VERSION=4
+    - NODEJS_VERSION=node/10 NAPI_VERSION=4
+    - NODEJS_VERSION=node/12 NAPI_VERSION=4
 matrix:
   fast_finish: true
-  allow_failures:
-    - env: NODEJS_VERSION=nightly
-    - env: NODEJS_VERSION=chakracore-nightly
 sudo: false
 cache:
   directories:
@@ -59,6 +51,8 @@ install:
 script:
   # Travis CI sets NVM_NODEJS_ORG_MIRROR, but it makes node-gyp fail to download headers for nightly builds.
   - unset NVM_NODEJS_ORG_MIRROR
+  - npm config set NAPI_VERSION $NAPI_VERSION
+  - npm config get NAPI_VERSION
 
   - npm test $NPMOPT
 after_success: