Update Travis CI parameters

Author: pandres95

.travis.yml

@@ -1,12 +1,8 @@
 services: mongodb
 language: node_js
 node_js:
-  - 4.0
-  - 5.0
-  - 6.0
-before_install:
-  - npm install -g npm@latest
+  - 8
 install:
-  - npm install bool.js@latest
+  - npm install booljs@latest
   - npm install mongoose
   - npm install