Move 'copyfiles' from devDependencies to dependencies

[KableM]

Currently installing pixi-lights as a dependency to another project fails because a post-install script attempts to use copyfiles:

sh: copyfiles: command not found
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! pixi-lights@2.0.0 copy: `copyfiles -f "node_modules/{pixi.js,pixi-layers}/dist/*.{js,map}" demo/lib`
npm ERR! spawn ENOENT
npm ERR! 
npm ERR! Failed at the pixi-lights@2.0.0 copy script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/kable/.npm/_logs/2018-05-15T06_36_56_803Z-debug.log
npm WARN pixi-test@1.0.0 No description
npm WARN pixi-test@1.0.0 No repository field.

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! pixi-lights@2.0.0 postinstall: `npm run copy`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the pixi-lights@2.0.0 postinstall 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!     /Users/kable/.npm/_logs/2018-05-15T06_36_56_833Z-debug.log

This PR simply moves copyfiles to 'prod' dependencies

[KableM]

Note Workaround in the meantime is to install copyfiles globally: npm i -g copyfiles before installing pixi-lights locally

[bigtimebuddy]

Thanks for this, but it’s not quite the right solution. The postinstall script should probably be removed (which calls copyfiles). I’ll look at it and see if there’s a better place for that.