fixed contribution docs

[mojoaxel]

This makes it possible to use the local version of gulp (from node_modeues/gulp) to build the library.
The current builds e.g. gulp build of course still work if gulp is globally installed. If gulp is only installed locally via npm install than the user should use npm run gulp to do the same.
This way it is possible to use different versions of gulb for different projects.

I also added the common npm build scripts: npm start and npm test, because they are a common go-to for new developers.

I hope you like these suggestions

[simonbrunel]

Thanks @mojoaxel for your suggestion.

This way it is possible to use different versions of gulb for different projects.

Only gulp-cli needs to be installed globally, which one use the local gulp defined in package.json. So that's already possible to use different versions of gulp for different projects:

chartjs> gulp --version
[18:01:57] CLI version 2.0.1
[18:01:57] Local version 4.0.0

chartjs-plugin-deferred> gulp --version
[18:05:20] CLI version 2.0.1
[18:05:20] Local version 3.9.1

Actually, the documentation is wrong, it should be:

> npm install
> npm install -g gulp-cli

I also added the common npm build scripts: npm start and npm test

I don't like the idea of mixing npm and gulp commands, it's confusing and at some point we will be asked to duplicate gulp commands to npm, which is useless and require more maintenance. Also, I don't think npm run gulp ... instead of gulp ... is the way we want to promote working in Chart.js sources.

[mojoaxel]

Only gulp-cli needs to be install globally

I had a lot of problems getting this to run with my current node (nvm) setup. 😡
Now after cleaning all global modules and reinstalling glob-cli globally it finally works. 😄

To be honest I'm not a big fan of installing things globally, but I guess that is a gulp thing.

I'll fix at least the docs...

I don't like the idea of mixing npm and gulp commands

I see 😐
I'm going to remove the scripts from this PR.

[mojoaxel]

Ok, at least I fixed the docs 😉

[simonbrunel]

Thanks @mojoaxel

I'm not fan either of installing stuff globally :) but I think it works pretty well for gulp-cli and I'm not sure it worth trying to get rid of it or creating npm run aliases for every gulp commands (it's also shorter using gulp). And have a partial mix of both doesn't sound great to me.

[simonbrunel]

Thanks @mojoaxel