refactor: use node-sass cli instead of grunt-sass (#2065)

Gruntfile.coffee

@@ -2,10 +2,6 @@ module.exports = (grunt) ->
     require('load-grunt-tasks') grunt, pattern: ['grunt-contrib-*', 'grunt-sass']
 
     grunt.initConfig
-        watch:
-          sass:
-            tasks: 'sass'
-            files: ['src/scss/*.scss']
 
         jshint:
           c3: 'src/**/*.js'
@@ -24,13 +20,5 @@ module.exports = (grunt) ->
             src: 'c3.css'
             dest: 'c3.min.css'
 
-        sass:
-          options:
-            sourcemap: 'none'
-          c3:
-            files:
-              'c3.css': 'src/scss/main.scss'
-
     grunt.registerTask 'lint', ['jshint']
-    grunt.registerTask 'build', ['concat', 'sass']
     grunt.registerTask 'minify', ['cssmin', 'uglify']

package.json

@@ -7,7 +7,9 @@
     "serve": "static -p 8080 htdocs/",
     "prepublish": "npm run dist",
     "lint": "grunt lint",
-    "build": "rollup -f umd --name c3 --globals d3:d3 src/index.js > c3.js",
+    "build": "npm run build:js && npm run build:css",
+    "build:js": "rollup -f umd --name c3 --globals d3:d3 src/index.js > c3.js",
+    "build:css": "node-sass src/scss/main.scss > c3.css",
     "minify": "grunt minify",
     "test": "npm run build && npm run lint && karma start karma.conf.js",
     "dist": "npm run build && npm run minify",
@@ -36,8 +38,6 @@
     "grunt-contrib-cssmin": "^0.10.0",
     "grunt-contrib-jshint": "^1.0.0",
     "grunt-contrib-uglify": "~0.4.0",
-    "grunt-contrib-watch": "^0.6.1",
-    "grunt-sass": "^2.0.0",
     "jasmine-core": "^2.3.4",
     "jshint-stylish": "^2.1.0",
     "karma": "^0.13.10",
@@ -46,6 +46,7 @@
     "karma-phantomjs-launcher": "^0.2.1",
     "karma-spec-reporter": "0.0.20",
     "load-grunt-tasks": "~0.2.0",
+    "node-sass": "^4.5.3",
     "node-static": "^0.7.9",
     "phantomjs": "^1.9.18",
     "rollup": "^0.41.6"