Update MochaJS to latest version

[SimonSimCity]

In order to keep up with the latest version of MochaJS (and specially for the issue mochajs/mocha#2095 which often ruined the report of my client-tests) I decided to take a look at how we could integrate its latest version.

As https://github.com/practicalmeteor/meteor-mocha-core seems to be abandoned (open PRs are left without any further notification for a long time), I've created a fork on this user (https://github.com/meteortesting/meteor-mocha-core). I first updated to MochaJS in version 3.5.3 and raised the version number to 1.0.1 - MochaJS 4.x.x doesn't seem to support PhantomJS anymore - at least my tests failed (see: Meteor-Community-Packages/meteor-mocha-core#1).

Since the tests only failed in PhantomJS, and the owner of the project decided to has archive it (ariya/phantomjs#15344), I decided to move on and see how far I can get.

I went straight to version 5.2.0, which is the latest as of the time writing, and committed it as a proposal for a 1.0.2 which works great using puppeteer as browser, which is as easy to add as PhantomJS.

Some ideas (some unresolved) still in my head where I want your opinion on:

• Publish https://github.com/meteortesting/meteor-mocha-core in version 1.0.0, 1.0.1 and 1.0.2 on atmosphere, so people could fix their project to e.g. 1.0.1 by locally requiring the package if they still need to support PhantomJS.
• I haven't settled on a versioning for https://github.com/meteortesting/meteor-mocha-core yet. One idea was to use the same version as MochaJS, as this is just a very thin wrapper - but it is a wrapper which itself also can contain bugs, that's why I'm unsure.
• Should we wait for our changes in https://github.com/meteortesting/meteor-mocha-core to get merged back or just take it on from here? If we go for maintaining it ourselves, I'd also take the open PRs over there and take it into our repository.
• Maybe We should follow Selenium and deprecate PhantomJS by including a warning (see: SeleniumHQ/selenium@b3daa03), or should we rather go for fixing Update to mocha 4.x meteor-mocha-core#1?

[aldeed]

@SimonSimCity I agree with all of that plan. For versioning the fork of core, Meteor allows you to use an underscore, so a common pattern is <wrapped_package_version>_<additional integer>. i.e. you could publish the one wrapping 5.2.0 as 5.2.0_1 and if you need to republish a change that doesn't change which mocha is wrapped, it would be 5.2.0_2. See the description for version option here: https://docs.meteor.com/api/packagejs.html#PackageNamespace-describe

[SimonSimCity]

@aldeed I've now updated the PR. Could you please merge it or grant me access to do so, and also the permission to update the repository?