Added grunt-update-json

[ff6347]

As requested in #372 for easy bower handling

[ff6347]

Tags created on a fork are not part of a pull request. To get this fully working with bower you still need to create tag "0.3.7" and push it to the bower registry:

# if bower is not installed  
npm install -g bower
# then
bower register p5js https://github.com/lmccart/p5.js.git 

[lmccart]

great, thanks!