Fix error when this npm module user installs

[lulzneko]

An error occurs when installing validate-typescript.
This pull request is a fix that avoids the error.

username@PC:~/project$ npm install validate-typescript

> validate-typescript@4.0.0 install ~/project/node_modules/validate-typescript
> cd test && npm install

sh: 1: cd: can't cd to test
npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! validate-typescript@4.0.0 install: `cd test && npm install`
npm ERR! Exit status 2
npm ERR!
npm ERR! Failed at the validate-typescript@4.0.0 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     ~/.npm/_logs/2019-03-13T25_67_89_000Z-debug.log

This error is because I've run npm install validate-typescript, which chained calls to the downloaded validate-typescript package's install.
(And the downloaded validate-typescript package does not have a test directory)

Empty the validate-typescript install script to avoid errors.
And I created a setup script that does the same thing as the current install script does.
Please run npm run setup when developing validate-typescript.
This is equivalent to the current npm install.

The same process as the current install script is moved to the setup name.
It contains npm install, so it can do the same thing as the current install script.
When developing validate-typescript, npm run setup can do the same as npm install.

Thank you for the great product.

[grant-zietsman]

Thanks, you should be able to run npm install validate-typescript without an error now. (v4.0.1)

[lulzneko]

Thank you for the quick merge and release !
Our project was also installed correctly 😄