Webpack upgrade

[jishnu7]

Pull request to upgrade webpack and babel to respective latest versions. All test cases are working.

There is an issue with coverage. Istanbul doesn't support ES6-Babel properly, we will have to use either babel-istanbul or isparta. Since master branch is using a custom fork of istanbul, I'm letting you decide on how to proceed with it.

Another way to handle is, running test cases on original source rather than the babel generated one. If we are going to do that, then we don't need grunt-babel, we will be able to use babel-loader with webpack to generate just the dist files we need, rather than exporting all transpiled sources.

Relates to: #1386 , #1399 ,

[nknapp]

That sounds great. remap-istanbul would be another option. I have used it in a TypeScript-project and it worked fine. It needs node 6 though, but that is another discussion.

In any case, could you point your PR to the 4.x-branch? That is the branch of currently released versions. There has not been a release of the master branch yet. I'll merge into the master from 4.x then.

4.x is not using the custom fork of istanbul, so babel-istanbul might work fine.

[jishnu7]

Made necessary changes and target branch to v4.x.

Using babel-istanbul straight away cleared the coverage except branches, which is having 99.91% coverage. Only one branch is not covered, but the interface is not clearly pointing out which section of the file is causing the issue. I'm checking if we can do something about it.

[jishnu7]

amd build seems to be failing because of dynamic import. master branch doesn't seems to have amd builds. Do you use amd build anywhere?

[nknapp]

I don't know how many users Handlebars has, but I think the pobability that someone uses amd-builds, is pretty high.

[nknapp]

I'll close this for now. Thanks for trying back then. I think, with some more integration tests we can do another attempt, but not now.