Replace deprecated react-tools with babel

- Switch to babel, since react-tools has been deprecated since June 12,
2015. See
https://facebook.github.io/react/blog/2015/06/12/deprecating-jstransform
-and-react-tools.html

- Move babel command to "npm run build"

- Move commands for package into "bin/package.js"

bin/check-deps.js

@@ -45,7 +45,7 @@ var BUILT_IN_ELECTRON_MODULES = [ 'electron' ]
 
 var BUILT_IN_DEPS = [].concat(BUILT_IN_NODE_MODULES, BUILT_IN_ELECTRON_MODULES)
 
-var EXECUTABLE_DEPS = ['gh-release', 'standard', 'react-tools']
+var EXECUTABLE_DEPS = ['gh-release', 'standard', 'babel-cli', 'babel-preset-react']
 
 main()