update npm from 7.6 to 8.0

Author: wrmswindmill

.travis.yml

@@ -1,6 +1,6 @@
 os: linux
 language: node_js
-node_js: 7.6
+node_js: 8.0
 matrix:
     fast_finish: true
     include:
@@ -74,7 +74,7 @@ install:
   - |
     if [[ ("$TEST_SUITE" = "android") || ("${ANDROID_LINT}" = "true") ]]; then
         curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.34.0/install.sh | bash
-        nvm install 7.6
+        nvm install 8.0
         npm install
         echo y | sdkmanager "cmake;3.6.4111459"
         if find "${HOME}/android-ndk-r18b" -mindepth 1 | read; then