Restructure prep-release script slightly

Order of operations is now:
- regenerate local assets
- clean the release dir
- download linux/windows releases
- build osx release
- smoke all test releases

// FREEBIE

Gruntfile.js

@@ -408,7 +408,7 @@ module.exports = function(grunt) {
   grunt.registerTask('test', ['jshint', 'jscs' ]);
   grunt.registerTask('copy_dist', ['gitinfo', 'copy']);
   grunt.registerTask('date', ['gitinfo', 'getExpireTime']);
-  grunt.registerTask('prep-release', ['gitinfo', 'fetch-release', 'test-release']);
+  grunt.registerTask('prep-release', ['gitinfo', 'clean-release', 'fetch-release']);
   grunt.registerTask('default', ['concat', 'sass', 'date']);
 
 };

package.json

@@ -49,7 +49,7 @@
     "build-mas-release": "npm run build-release -- -m --config.mac.target=mas",
     "build-mas-dev": "npm run build-release -- -m --config.mac.target=mas --config.type=development",
     "prep-mac-release": "npm run build-release -- -m --dir",
-    "prep-release": "grunt clean-release && npm run generate && npm run prep-mac-release && npm run build-mas-release && grunt prep-release",
+    "prep-release": "npm run generate && grunt prep-release && npm run build-release && npm run build-mas-release && grunt test-release",
     "release-mac": "npm run build-release -- -m --prepackaged release/mac/Signal.app --publish=always",
     "release-win": "npm run build-release -- -w --prepackaged release/win-unpacked --publish=always",
     "release-lin": "npm run build-release -- -l --prepackaged release/linux-unpacked && VERSION=$npm_package_version ./aptly.sh",