Arrange docs for publishing github pages

[takerfume]

I arranged the directory 'machina/docs'.

• I move source files in the directory machina/docs/source
• I added index.html in 'machina/docs'.

@rarilurelo Could you set the master branch /docs folder as machina's GitHub Pages publishing source like this explanation?

Then, we can probably see our docs page in https://deepx.github.io/machina/.