chore: rm yarn.lock, add lock files to .gitignore (#131)

* chore(lock): Sync yarn.lock changes on clean install

The package dependency version for `babel-cli` are out of sync in `package.json`(`6.24.1`) and
`yarn.lock`(`6.23.0`). Add changes made to lockfile by yarn after clean install

* chore: rm yarn.lock, add lock files to .gitignore

Remove yarn.lock and add yarn.lock, package-lock.json to .gitignore

* ci(travis): Use npm for running scripts

travis detects whether yarn is being used by looking for the lock file. Since the previous commit
removed yarn.lock, travis build would fail for script execution with yarn. Switch to npm to fix
build failure

.gitignore

@@ -4,3 +4,6 @@ dist
 .opt-in
 .opt-out
 
+# Lock files
+yarn.lock
+package-lock.json

.travis.yml

@@ -8,10 +8,10 @@ notifications:
 node_js:
   - '6'
 script:
-  - yarn start validate
+  - npm start validate
 after_success:
-  - yarn start report-coverage
-  - yarn start release
+  - npm start report-coverage
+  - npm start release
 branches:
   only:
     - master