Upgrade Project (#128)

**- Summary**
- upgrade to babel 7
- upgrade to eslint 5 (removed invalid rules too)
- updated other dependencies

**- Description for the changelog**

build: update dependencies

.babelrc

@@ -1,7 +1,9 @@
 {
-  "presets": ["env"],
+  "presets": [
+    "@babel/preset-env"
+  ],
   "plugins": [
-    "syntax-object-rest-spread",
-    "transform-object-rest-spread"
+    "@babel/plugin-syntax-object-rest-spread",
+    "@babel/plugin-proposal-object-rest-spread"
   ]
 }

.eslintrc → .eslintrc.yml

@@ -3,25 +3,10 @@ env:
 
 parser: babel-eslint
 
-plugins: [ "import" ]
+parserOptions:
+  ecmaVersion": 6
 
-# enable ECMAScript features
-ecmaFeatures:
-  arrowFunctions: true
-  binaryLiterals: true
-  blockBindings: true
-  classes: true
-  defaultParams: true
-  destructuring: true
-  forOf: true
-  generators: true
-  jsx: true
-  modules: true
-  objectLiteralShorthandMethods: true
-  objectLiteralShorthandProperties: true
-  octalLiterals: true
-  spread: true
-  templateStrings: true
+plugins: [ "import" ]
 
 rules:
   # Possible Errors

gulpfile.babel.js

@@ -6,7 +6,7 @@ import pluginError from "plugin-error";
 import flatten from "gulp-flatten";
 import postcss from "gulp-postcss";
 import cssImport from "postcss-import";
-import cssnext from "postcss-cssnext";
+import postcssPresetEnv from "postcss-preset-env";
 import BrowserSync from "browser-sync";
 import webpack from "webpack";
 import webpackConfig from "./webpack.conf";
@@ -32,7 +32,7 @@ gulp.task("build-preview", ["css", "js", "fonts"], (cb) => buildSite(cb, hugoArg
 // Compile CSS with PostCSS
 gulp.task("css", () => (
   gulp.src("./src/css/*.css")
-    .pipe(postcss([cssImport({from: "./src/css/main.css"}), cssnext()]))
+    .pipe(postcss([cssImport({from: "./src/css/main.css"}), postcssPresetEnv()]))
     .pipe(gulp.dest("./dist/css"))
     .pipe(browserSync.stream())
 ));