Drop "uglify": true from babel targets

[ojab]

uglify-es (that supports es6) is used since 3.2.1, so we shouldn't downgrade js features to the ones supported by non-es uglify.

[danielpowell4]

At very least with this PR, it would be better to use "forceAllTransforms": true, over "uglify": true

Reference:
https://babeljs.io/docs/plugins/preset-env/#targetsuglify

[ojab]

This option is not available in babel-preset-env-1.x (which is used right now).
I assume that babel-preset-env-2.0 w/ "uglify" removed and "forceAllTransforms" added will be released along babel-7 and this option basically mirrors "uglify": true, downgrading js features to es5.

[gauravtiwari]

@ojab Please correct me if I misunderstood the change, from plugin docs page, uglify option is available in 1.x but deprecated and replaced with forceAllTransforms in 2.x. We are still using 1.6.1 so the uglify option is still valid.

Anyway, I think what you want to change here is remove uglify option since we support es6 syntax by default right?

[ojab]

Yep, correct.