Feature/milestone 4/116 generate button implementation

[trinitytakei]

The whole flow works now:

• entering the name of the app into the text field
• it's checking the availability of the repo under your github account; prevents the app generation if the repo exists
• if it's available, and you hit "Generate my app", it generates the app and pushes it to Github

It's probably rough around the edges, but wanted to merge it nevertheless as it was too long in the tooth.

[trinitytakei]

LGTM