UglifyJs: Change the ecma option from 8 to 5

[LubomirGeorgiev]

Problem:

I recently had a problem with the ecma option of UglifyJs being set to 8.

One of my packages was using bn.js as a dependency and this block of code right here was compiled to return{a,b:f,gcd:i.iushln(c)}} and of course the a threw an SCRIPT1003: Expected ':' error in Internet Explorer because it doesn't support the new EcmaScript 6 Property Shorthand syntax. I had no idea what it was and how to fix it until I found this solution so that's why I am fixing it here in this repo.

Solution:

To change the ecma option of UglifyJS from 8 to 5 to ensure maximum compatibility with older browsers.

I think it's not very safe to keep it at 8 because not all browsers are fully EcmaScript 8 and even 6 compatible yet.

[retlehs]

thank you!