Add ability to initialize cypress directory programmatically

[drewbrend]

Current behavior:

To populate the /cypress/ directory you must open cypress GUI after it is installed

Desired behavior:

Be able to run a command from the CLI to populate the /cypress/ directory, something like cypress init.

Reasoning for this:

My company has an internal npm package we have created that contains additional commands, plugins, fixtures, etc for our application. npm install finishes with a postinstall script will "plug" this into files in the /cypress/ directory. Example: adding an import statement to the support/index.js file, and adding a call to our shared package's plugins/index.js file from the application's plugins/index.js file.

In a new project, the setup workflow for us is:

1. npm install --save-dev cypress
2. ./node_module/.bin/cypress open <= solely to populate the /cypress/ directory
3. npm install --save-dev @ourcompany/shared-cypress

If the user has not opened cypress and does not have the /cypress/ directory, we spew out a bunch of errors and tell them they need to open cypress and reinstall our package

If cypress has a command like cypress init, we could run that in a preinstall script and not have to worry about this case.

Versions

Cypress 3.1.0

[jennifer-shehane]

Duplicate of #619 Thanks for detailing your use case!