es6-promise-polyfill | ES6 Promise polyfill | Reactive Programming library

I have following js includes:

Hello guys I'm trying to learn Webpack I've been following some tutorials and I've run into some problems. I've installed webpack locally in folder I am working in with npm install webpack --save-dev. I made two JS scripts and I wanted to bundle them and I've tried following command webpack script-1.js /.bundle.js in WindowsPowerShell (I'm using Windows 7). Now this made the following error

webpack is not recognized as an internal or external command operable program or batch file

So then I installed webpack globally, and when I used the same command in PowerShell (I have opened it as an admin), it made bundle.js file but not in the directory I was working in, but in C:
Now after this failure I've decided to try using git bash. First I've tried this command webpack script-1.js /.bundle.js and got the following error

bash: webpack: command not found

Finally after some trying I was able to make it work using this command in git bash node_modules/.bin/webpack ./script-1.js bundle.js
Is there a way to fix this, so I can just type webpack instead of whole path ? Also is there a way to fix path in PowerShell ?

This is mine package.json