Drop support for node 4 / npm 2

(closes #4853)

This fixes several issues with dependency resolution

.travis.yml

@@ -1,6 +1,5 @@
 language: node_js
 node_js:
-  - "4"
   - "6"
   - "8"
 sudo: required

README.md

@@ -33,7 +33,7 @@ Come on in, the water's lovely. More help? Ping `jfire` or `bhousel` on:
 
 ## Prerequisites
 
-* [Node.js](https://nodejs.org/) version 4 or newer
+* [Node.js](https://nodejs.org/) version 6 or newer
 * [`git`](https://www.atlassian.com/git/tutorials/install-git/) for your platform
   * Note for Windows users:
     * Edit `$HOME\.gitconfig`:<br/>

build_src.js

@@ -5,7 +5,6 @@ const rollup = require('rollup');
 const nodeResolve = require('rollup-plugin-node-resolve');
 const commonjs = require('rollup-plugin-commonjs');
 const json = require('rollup-plugin-json');
-const includePaths = require('rollup-plugin-includepaths');
 const colors = require('colors/safe');
 const flowRemoveTypes = require('flow-remove-types');
 
@@ -30,11 +29,6 @@ module.exports = function buildSrc() {
                 input: './modules/id.js',
                 plugins: [
                     flow(),
-                    includePaths({
-                        paths: [
-                            'node_modules/d3/node_modules' // for npm 2
-                        ]
-                    }),
                     nodeResolve({
                         module: true,
                         main: true,
@@ -84,4 +78,4 @@ function flow() {
             map: null
         })
     };
-}
+}

modules/ui/field_help.js

@@ -6,7 +6,7 @@ import {
 import marked from 'marked';
 import { t } from '../util/locale';
 import { svgIcon } from '../svg';
-import { icon } from 'intro/helper';
+import { icon } from './intro/helper';
 
 
 // This currently only works with the 'restrictions' field

modules/ui/help.js

@@ -15,8 +15,7 @@ import { uiMapData } from './map_data';
 import { uiShortcuts } from './shortcuts';
 import { uiTooltipHtml } from './tooltipHtml';
 import { tooltip } from '../util/tooltip';
-
-import { icon } from 'intro/helper';
+import { icon } from './intro/helper';
 
 export function uiHelp(context) {
     var key = t('help.key');

package.json

@@ -69,7 +69,6 @@
     "request": "^2.85.0",
     "rollup": "~0.57.0",
     "rollup-plugin-commonjs": "^9.0.0",
-    "rollup-plugin-includepaths": "^0.2.2",
     "rollup-plugin-json": "^2.2.0",
     "rollup-plugin-node-resolve": "^3.2.0",
     "shelljs": "^0.8.0",
@@ -89,6 +88,7 @@
     ]
   },
   "engines": {
-    "node": ">=4.0.0"
+    "node": ">=6.0.0",
+    "npm": ">=3.0.0"
   }
 }