Update setup guide for babel6

[lukabot]

First of all, thanks for the great tutorial.

I'm new to babel today, and I was unable to compile the code after following this setup guide.
After googling for a while, I found that babel now needs presets to compile.

So, I suggest to update setup guide to official setup guide.

1. Install babel as local installation, not global (for project management).
2. Mention about presets and .babelrc file.
   
   Adding this line might be better.
   
   npm install babel-preset-es2015 --save-dev

echo '{ "presets": ["es2015"] }' > .babelrc

[lukabot]

Opps, some bug here.
tower-of-babel run and tower-of-babel verify does not work with presets.

Could not run: [BABEL] ... Unknown option: .babelrc.presets

Any suggestions?

[yosuke-furukawa]

ya, I know the issue. I will fix asap.