As discussed in #370 and announced in the official Eslint-meteor
plugin repository (https://github.com/dferber90/eslint-plugin-meteor),
it is recommended to not use this plugin anymore has the author has it
is currently broken and the author has abandoned it.
This commit fixes the download link in the activity feed on the
sidebar and the mention link on card description and comments
(replaced by a popup).
`eslint .` now passes without any error or warning.
Fixes#286
Replace the old (and broken) jshint + jscsrc by eslint and configure
it to support some of the ES6 features.
The command `eslint` currently has one error which is a bug that was
discovered by its static analysis and should be fixed (usage of a
dead object).
