update babel-preset-es2015 to 6.18.0

[mziemer21]

I am getting an error when I try to run my webpack build.

Error in config file!
Error: Options {"loose":true} passed to /Users/my-repo/node_modules/babel-preset-es2015/lib/index.js which does not accept options.
(While processing preset: "/Users/my-repo/node_modules/babel-preset-es2015/lib/index.js")
(While processing preset: "/Users/my-repo/node_modules/babel-preset-es2015/lib/index.js")

This PR added { "loose": true } to es2015 preset, but loose is not supported until es2015 v6.13.0.

I updated babel-preset-es2015 to latest v6.18.0 and all the tests pass.

[mziemer21]

@benjamn @hzoo could someone take a look at this?

[kangax]

@hzoo looks good?

[hzoo]

Shouldn't be necessary given ^ but yeah 👍

[benjamn]

Does this warrant publishing a new npm version?

[hzoo]

In the OP, this is in reference to #265 which is about building regenerator itself so no I don't think so

[mziemer21]

@benjamn could you publish a new version? I am getting this error in a different repo's webpack build, not regenerator's.