Fix gulp + eslintrc ( inc. PR sparksuite#741 )

This commit includes the fixes introduced in Pull Request sparksuite#741 ( sparksuite#741 )
that were added by @roipoussiere

It also includes these extra improvements:

 - Added lines for `no-redeclare` and `no-prototype-builtins` to `.estlintrc` which are set to disable warnings and errors for
   (re-)declaring global variables/functions like `require`, and disabling errors/warnings for prototyping built-ins
   e.g. extending `Object` - This was required for `gulp browserify` to build the scripts without errors

 - Added `yarn.lock` to lock package versions for those of you who use `yarn` instead of `npm` :)

.eslintrc

@@ -13,11 +13,14 @@
     "semi": [
       2,
       "always"
-    ]
+    ],
+    "no-redeclare": [2, {"builtinGlobals": false}],
+    "no-prototype-builtins": 0,
+    "no-useless-escape": "off"
   },
   "env": {
     "browser": true,
     "node":true
   },
   "extends": "eslint:recommended"
-}
+}

gulpfile.js

@@ -22,48 +22,49 @@ var banner = ["/**",
 	" */",
 	""].join("\n");
 
-gulp.task("prettify-js", [], function() {
+gulp.task("prettify-js", function(done) {
 	return gulp.src("./src/js/simplemde.js")
 		.pipe(prettify({js: {brace_style: "collapse", indent_char: "\t", indent_size: 1, max_preserve_newlines: 3, space_before_conditional: false}}))
 		.pipe(gulp.dest("./src/js"));
 });
 
-gulp.task("prettify-css", [], function() {
+gulp.task("prettify-css", function() {
 	return gulp.src("./src/css/simplemde.css")
 		.pipe(prettify({css: {indentChar: "\t", indentSize: 1}}))
 		.pipe(gulp.dest("./src/css"));
 });
 
-gulp.task("lint", ["prettify-js"], function() {
+gulp.task("lint", gulp.series("prettify-js", function(done) {
 	gulp.src("./src/js/**/*.js")
 		.pipe(debug())
 		.pipe(eslint())
 		.pipe(eslint.format())
 		.pipe(eslint.failAfterError());
-});
+	done();
+}));
 
 function taskBrowserify(opts) {
 	return browserify("./src/js/simplemde.js", opts)
 		.bundle();
 }
 
-gulp.task("browserify:debug", ["lint"], function() {
+gulp.task("browserify:debug", gulp.series("lint", function() {
 	return taskBrowserify({debug:true, standalone:"SimpleMDE"})
 		.pipe(source("simplemde.debug.js"))
 		.pipe(buffer())
 		.pipe(header(banner, {pkg: pkg}))
 		.pipe(gulp.dest("./debug/"));
-});
+}));
 
-gulp.task("browserify", ["lint"], function() {
+gulp.task("browserify", gulp.series("lint", function() {
 	return taskBrowserify({standalone:"SimpleMDE"})
 		.pipe(source("simplemde.js"))
 		.pipe(buffer())
 		.pipe(header(banner, {pkg: pkg}))
 		.pipe(gulp.dest("./debug/"));
-});
+}));
 
-gulp.task("scripts", ["browserify:debug", "browserify", "lint"], function() {
+gulp.task("scripts", gulp.series("browserify:debug", "browserify", "lint", function() {
 	var js_files = ["./debug/simplemde.js"];
 
 	return gulp.src(js_files)
@@ -72,9 +73,9 @@ gulp.task("scripts", ["browserify:debug", "browserify", "lint"], function() {
 		.pipe(buffer())
 		.pipe(header(banner, {pkg: pkg}))
 		.pipe(gulp.dest("./dist/"));
-});
+}));
 
-gulp.task("styles", ["prettify-css"], function() {
+gulp.task("styles", gulp.series("prettify-css", function() {
 	var css_files = [
 		"./node_modules/codemirror/lib/codemirror.css",
 		"./src/css/*.css",
@@ -91,6 +92,6 @@ gulp.task("styles", ["prettify-css"], function() {
 		.pipe(buffer())
 		.pipe(header(banner, {pkg: pkg}))
 		.pipe(gulp.dest("./dist/"));
-});
+}));
 
-gulp.task("default", ["scripts", "styles"]);
+gulp.task("default", gulp.series("scripts", "styles"));