Convert into a yeoman generator

[eirikurn]

yo aranja-webapp?

• Use placeholders for project name across the base
• If there are different ways to setup the base, they should be added as generator options (e.g. should there be a server task)
• Should install and --save newest versions of all the plugins IMHO

[thorsteinsson]

We could add more options to the gulp base if we have this, like choosing between less, sass and stylus for example.