chore: update gitignore (#1527)

We are removing validator.js and validator.min.js since they are among
the top files that cause unnecessary conflicts, yet they are dependent
on the build system.

this is a follow up of #1450

Author: profnandaa

.gitignore

@@ -7,3 +7,5 @@ package-lock.json
 yarn.lock
 /es
 /lib
+validator.js
+validator.min.js

.travis.yml

@@ -12,4 +12,5 @@ notifications:
   email: false
 after_success:
   - npm install -g codecov
+  - npm run build
   - npm run test:ci > coverage.lcov && codecov