remove node 6 support

This reverts commit 7d4049f
and disables running tests in travis on node 6 and specifies engine support in package.json

Author: gdelmas

.travis.yml

@@ -6,7 +6,6 @@ env:
   - GIT_AUTHOR_EMAIL=yosuke.kurami@gmail.com
 language: node_js
 node_js:
-- 6
 - 8
 - 9
 before_script:

package.json

@@ -24,6 +24,9 @@
   ],
   "author": "quramy",
   "license": "MIT",
+  "engines": {
+    "node": ">=8.0.0"
+  },
   "dependencies": {
     "camelcase": "^5.3.1",
     "chalk": "^2.1.0",

src/DtsContent.ts

@@ -1,8 +1,11 @@
+import * as fs from "fs";
 import * as os from "os";
 import * as path from "path";
 import isThere from "is-there";
 import * as mkdirp from 'mkdirp';
-import {writeFile} from "./fs";
+import * as util from "util";
+
+const writeFile = util.promisify(fs.writeFile);
 
 
 interface DtsContentOptions {
@@ -71,7 +74,7 @@ export class DtsContent {
             mkdirp.sync(outPathDir);
         }
 
-        await writeFile(this.outputFilePath, this.formatted);
+        await writeFile(this.outputFilePath, this.formatted, 'utf8');
     }
 }
 

src/FileSystemLoader.ts

@@ -1,15 +1,18 @@
 /* this file is forked from https://raw.githubusercontent.com/css-modules/css-modules-loader-core/master/src/file-system-loader.js */
 
 import Core from 'css-modules-loader-core'
+import * as fs from 'fs'
 import * as path from 'path'
+import * as util from 'util'
 import { Plugin } from "postcss";
-import {readFile} from "./fs";
 
 
 type Dictionary<T> = {
   [key: string]: T | undefined;
 };
 
+const readFile = util.promisify(fs.readFile);
+
 
 export default class FileSystemLoader {
   private root: string;
@@ -51,7 +54,7 @@ export default class FileSystemLoader {
       }
 
       try {
-        source = await readFile(fileRelativePath);
+        source = await readFile(fileRelativePath, "utf-8");
       }
       catch (error) {
         if (relativeTo && relativeTo !== '/') {