[ Update ] Eloquent.md
[ Update ] Eloquent.md

I've just figured it out that laravel has got an awesome method called `updatePivotTable` so I put a little documentation under `Working with Pivot table`.

Let me know if everything is correct :smile:
tusharvikky/docs,tusharvikky/docs,laravel-china/laravel-docs,iwzh/laravel-docs,ryanwinchester/laravel-docs,xpressengine/laravel-korean-docs,iwzh/laravel-doc-offline,xpressengine/laravel-korean-docs,ryanwinchester/laravel-docs,khs1994-gitbook/laravel-docs,chenrenzhen/laravel-docs-china