fix(gulp): Removed unused plugins

Author: dlabrecq

gulpfile.js

@@ -5,15 +5,13 @@ var gulp = require('gulp'),
   cssmin = require('gulp-cssmin'),
   csso = require('csso'),
   del = require('del'),
-  exec = require('child_process').exec,
   fs = require("fs"),
   htmlMinifier = require('html-minifier'),
   lessCompiler = require('gulp-less'),
   ngc = require('gulp-ngc'),
   path = require('path'),
   postcss = require('postcss'),
   replace = require('gulp-replace'),
-  runSequence = require('run-sequence'),
   sourcemaps = require('gulp-sourcemaps'),
   stylus = require('stylus');