Run styles and scripts in sequence

Prevents potential race condition where styles and scripts write to the
manifest at the same time

ref https://github.com/roots/sage/issues/1398

Updates changelog

gulpfile.js

@@ -6,6 +6,7 @@ var browserSync = require('browser-sync');
 var gulp        = require('gulp');
 var lazypipe    = require('lazypipe');
 var merge       = require('merge-stream');
+var runSequence = require('run-sequence');
 
 // See https://github.com/austinpray/asset-builder
 var manifest = require('asset-builder')('./assets/manifest.json');
@@ -236,7 +237,12 @@ gulp.task('watch', function() {
 // ### Build
 // `gulp build` - Run all the build tasks but don't clean up beforehand.
 // Generally you should be running `gulp` instead of `gulp build`.
-gulp.task('build', ['styles', 'scripts', 'fonts', 'images']);
+gulp.task('build', function(callback) {
+  runSequence('styles',
+              'scripts',
+              ['fonts', 'images'],
+              callback);
+});
 
 // ### Wiredep
 // `gulp wiredep` - Automatically inject Less and Sass Bower dependencies. See