mocha not found on Travis CI

[georgeOsdDev]

Travis CI build start failing from #190, #191

It seems lerna bootstrap is not called as postinstall after npm ci.

Success case:
https://travis-ci.com/github/mobilusoss/textlint-browser-runner/builds/191070080

npm ci 
> husky@4.3.0 install /home/travis/build/mobilusoss/textlint-browser-runner/node_modules/husky
> node husky install
husky > Setting up git hooks
CI detected, skipping Git hooks installation.
husky > Done
> husky@4.3.0 postinstall /home/travis/build/mobilusoss/textlint-browser-runner/node_modules/husky
> opencollective-postinstall || exit 0
> root@undefined postinstall /home/travis/build/mobilusoss/textlint-browser-runner
> lerna bootstrap
lerna notice cli v3.22.1
lerna info ci enabled
lerna info Bootstrapping 4 packages
lerna info Installing external dependencies
lerna info Symlinking packages and binaries
lerna success Bootstrapped 4 packages
added 944 packages in 20.434s

Fail case:
https://travis-ci.com/github/mobilusoss/textlint-browser-runner/builds/191564613

$ npm ci 
added 946 packages, and audited 946 packages in 6s
5 high severity vulnerabilities
To address issues that do not require attention, run:
  npm audit fix
Some issues need review, and may require choosing
a different dependency.
Run `npm audit` for details.

[georgeOsdDev]

npm/cli#1905

[georgeOsdDev]

fixed with #193