Add release script

Author: guggero

.gitignore

@@ -1,3 +1,4 @@
 .idea
 node_modules
 yarn-error.log
+release

package.json

@@ -46,6 +46,8 @@
   },
   "scripts": {
     "browserify": "browserify -o libs/js/bitcoin.js browserify.js --standalone bitcoin",
-    "templates": "grunt ngtemplates"
+    "templates": "grunt ngtemplates",
+    "maketargz": "tar --exclude=release --exclude=.idea --exclude=node_modules -czvf release/cryptography-toolkit.offline.tar.gz *",
+    "release": "rm -rf release && mkdir release && yarn maketargz && cd release && sha256sum -b * > cryptography-toolkit.offline.sum"
   }
 }